Paragraph (1) of Article 33 in the Constitution provides all workers with the right to collective action in order to enhance working conditions. For securing the right to collective action pursuant to the Constitution, the Trade Union and Labor Relations Adjustment Act(hereafter ``the Act``) confirms the protections for "industrial action" which means actions or counter-actions that obstruct the normal operation of a business, such as strikes, sabotage, lock-outs, or other activities through which the parties to labor relations intend to achieve their claims; restriction on civil claims for damages because of industrial action(article 3),limitation of criminal claims against industrial action of trade unions(article 4) and prohibition of dismissal of or discrimination against a worker on the grounds of participation in lawful collective activities(subsection 5 of article 81).The Supreme Court, however, has decided that all kinds of protections under the Act could be given only in the case that the industrial action might satisfy with four requirements of ``lawful industrial action``: 1) the industrial action should be begun and led by a body which must be qualified to a representative in collective bargaining such as a trade union; 2) the purposes of the industrial action should be to facilitate self-governing negotiation or bargaining between labor and management for the enhancement of working terms and conditions; 3) the industrial action should be begun only after the employer rejected collective bargaining by the specific requests of workers and it should obey the procedures required by applicable laws and regulations including vote of majority of union members for strike; 4) means or ways of industrial action should be harmonized with the employer`s property right and shall not take any exercise of violence. Because of these restricted legitimacy of case law, a strike might be illegal very easily. This paper argues that the case laws concerning industrial action have gone beyond the protection of the right to collective action under the Constitution so that they have to be changed. Dealing with the problems concerning as the effect of industrial action to employment relationship, the Court has taken a theory of ``suspension of employment relationship``. According to the theory, the parties of employment contract, an employee and an employer, should not fulfill each one`s primary duty; duty to work of an employee and duty to pay a wage of an employer. The Court have also required the four conditions of ``lawful industrial action`` in application of ``suspension of employment relationship`` effect. This paper argues that an interpretation of employment relationship during industrial action should be changed into the way harmonized with the purpose of protection of the right to collective action.