A seedling transplanter is provided to transplant seedlings of plural rows properly according to an inclined state of the surface of a ridge though the surface of the ridge is not horizontal. A seedling transplanter includes: the seedling transplanting parts(20) for transplanting the seedlings on a ridge while moving up and down along a certain operating trace by a vertical moving machine(21)； molding and hardening wheels(37) respectively installed on the rear of the seedling transplanting parts； a left and right slope sensor for detecting a height difference of left and right directions of the ridge by a height difference of the molding and hardening wheels； and a control unit for controlling a height of the ridge of the seedling transplanting parts to a certain height based on the detected height difference.
