To provide a simple angle adjusting device capable of speedily and precisely carrying out angle adjustment and fixture of a rotating side part in work with one hand and without using any special tool, etc.

A bolt 24 with a groove to fix a rotating side part 21 on a fixing side part 22 by preventing movement in the rotating direction A around a rotary shaft member 23 as its center as it is screwed in the rotating side part 22 through the rotating side part 21 and a contact part 26 formed on the rotating side part 21 and free to make contact with a tool of the bolt 24 with the groove are provided, and when the tool is oscillated in the rotating direction A around a fitting end as its center while the fitting end of the tool is fitted in the groove of the bolt 24 with the groove, the tool makes contact with the contact part 26 and pressurizes the rotating side part 21 in the rotating direction A.