To provide a technique contributing to the improvement of usability when the inclination angle of a circular saw body part is adjusted.

In a portable circular saw, a regulation device 181 regulating the circular saw body part at a plurality of usual inclination angle positions is installed. The regulation device 181 is composed of a plurality of step parts 181a-181d installed in the circular saw body part to correspond to each usual inclination angle position and an engagement member 183 which is installed on the side of a base 111 and regulates the inclination angle of the circular saw body part at a usual inclination angle corresponding to a selected step part. In the engagement member, by moving in the axial direction, the amount of projection is different between a plurality of projection positions corresponding to the number of the steps of the step parts 181a-181d. By changing the projection positions, engagement in relation to the step parts 181a-181d is selected.