To apply tension to a belt 46 in a reciprocating body driving device 40 which has a main rope 3 with a car and a counter weight connected thereto and a sheave 42 with the main rope 3 wound therearound, and drives the main rope 3 in the longitudinal direction thereof by pressing a part the sheave 42 with the main rope 3 wound therearound by the belt 46 of a circulating belt transmission mechanism.

The reciprocating body driving device has a lever 11 which has a pulley 45 pivotably attached thereto and is turnably provided on a frame 41 by a shaft 12. A bolt 13 fixed to the frame 41 and a coned disk spring 14 between the bolt 13 and the lever 11 are provided, and a spherical seat 20 is provided between the coned disk spring 14 and the lever 11.