To provide a coupler installation structure for a low-floor vehicle improving design property and manufacturing property by simplifying a structure of a base frame 2 by eliminating a level difference part from the base frame 2 by installing a coupler 3 above the base frame 2 or reducing a level difference of the level difference part and capable of attaining weight reduction of the base frame 2.

In the low-floor vehicle including the coupler 3 on an end part in a longitudinal direction of a vehicle 1, the coupler 3 is installed above the base frame 2 arranged near a driving room 1b of leading vehicles 11, 11 at a front side and a rear side.