To provide a lever handle shaft engaging structure which can easily assemble a square shaft with a simple structure without increasing the number of components and can reduce looseness only by the insertion of the square shaft.

In the lever handle shaft engaging structure for the square shaft 25 to the end part of which a lever handle 21 is fitted and a cam member rotatably provided to a lock box and having a square hole, recessed grooves 37 along the direction of the shaft line 35 are formed on at least two side surfaces 25a, 25b along the shaft line direction of the square shaft 25 in a longitudinal direction of the square shaft 25. Both leg parts 39a, 39b of a linear spring member 33 bent in substantially a U-shape are engaged in the two recessed grooves 37, while curved parts 41, 41 projecting from the side surfaces 25a, 25b and coming into contact with the inner surfaces are provided at the positions of the linear spring member 33 facing the inner surface of the square hole.