To provide a crawler tension regulating device easy to be assembled and having simple structure, without the possibility of damaging constitutional members.

On one side of a front and rear direction of an idler support member 12 rotatably supporting an idler 14 on the other side of the front and rear direction and provided in a guide part 11 of a truck frame 10 to be movable in the front and rear direction, a support plate 40 for supporting the idler support member 12 is provided to be movable in the front and rear direction by being engaged to the guide part 11. The support plate 40 is divided into a plurality of the plates 40, and the plurality of plates 40 are attachably/detachably mounted. It is desirable that a groove part 17 of a peripheral direction fitted with the support plates 40 is provided at the other end part of the idler support member 12.