An endoscope operation portion structure includes: a frame member inserted from an opening portion on an operation portion main body and arranged; a first fixing portion formed such that a length between a first apex protruded from one side of the frame member and a point on another side opposed to the first apex is longer than a long side of the opening portion; and a second fixing portion formed such that a length between a second apex protruded from the other side of the frame member and a point on the one side opposed to the second apex is longer than the long side of the opening portion, wherein the length between the first apex and the point on the other side and the length between the second apex and the point on the one side portion are shorter than a diagonal direction of the opening portion.