To provide the improved structure of an existing gravity type quay which reduces a period of the occupation of the quay in construction work, allows the arbitrary setting of the position of locking a tie member to a bracing according to conditions, and effectively offers sufficient strength against the toppling moment.

The improved structure of the existing gravity type quay constructed by sinking a caisson 2 at a water edge includes the newly built bracing 19 which is made by filling a cylindrically shaped steel plate 20a with concrete 22 and disposed closer to the land to be separated from the caisson across a given distance and has a lower end placed underground at a given depth, and the tie member 24 which is extended from a locking portion 30 formed on a top panel 10 at the upper end of the caisson toward a given level of the inside of the steel plate of the newly built bracing and whose both ends are anchored to the steel plate and to the locking portion of the top panel, respectively. The tie member is so set as to extend from the caisson toward the newly built bracing in a downwardly sloped position.