This study explored into the poetic spirit of ‘Sea’ in Ko Un’s poetry. He has been approaching ‘the poet of sea.’ His poetry after the 2000s has been broadened and constantly evolving in its prospect. This direction of evolution connotes the cognition of new poetic exploration about the current and wave of sea confronting a fixed culture and the downward earthly life. In 1950s, the country ruined by the war and Ko’s mental illness made his cognition of sea in his early poetry. His early poems involved existential agony of the whole generation with no outlook for the life. This existential futility was not ‘the imagination of despair’ through sea but the process to formate his volition above the despair. In 1970s, his poetry faced with ‘the death of Jeon Tae-il’ was broadened into political cognition with the volition for revolution of poetry rather than extinction of poetry. This was not sudden transition, but his poetic future, already born with sea in his inner poems. In the era of Man-in bo, His poetic aim went toward the cognition of the people’s life,the host of history, as future, hope, agony and grief of the torrent. Therefore, ‘sea’ was not the grave of death but the womb for life making historical life return to a primitive horizon. His poetic spirit of sea escaped oppression of earthly life and became recognized as sea of new birth. Furthermore, it was recognized as natural foresight or fruit of insight. ‘Sea’ was the torrent of the ground for him, and his literature, which the poetic destiny left with the sea, was also a torrent in the Korean history of literature. It made the womb, conceiving a new life with pain, live dynamically. Thus, he clamors the birth of poem for dynamic sea, telling ‘still we have to be born again.’As a result, the new poetic destiny cognizing ‘His sea’ goes toward the new poetic birth, involving the sea emerging from the view of land and expanding into the horizon. The route for ‘Sea’ for him was the poetic destiny desiring freedom of the new order and his future as well.