To provide a dovetail groove-dovetail type slide mechanism having a simple constitution and capable of easily displacing a movable side wall.

An dovetail groove 2 is formed on the rotary table 12 of a gonion stage and a dovetail 3 is formed in the main body. The dovetail groove 2 and the dovetail 3 are mutually fitted to each other, and one of two oblique side walls of the dovetail groove 2 is constituted of a movable side wall 4. In the dovetail groove-dovetail type slide mechanism in which the clearance between the dovetail groove 2 and the dovetail 3 is adjusted in the breadthwise direction of the dovetail groove, the movable side wall 4 is integrally connected to the extremity of a flexible thin sheet 5 extended from the inside bottom face of the dovetail groove 2, and one of the movable side wall 4 and the slide face of the dovetail 3 is defined by a protruded curved face bent in the direction orthogonal to the sliding direction of the rotary table 12. Thereby, the mutual contact in the vicinity of the breadthwise both ends of the slide face is avoided.