According to one embodiment, an angle variable mechanism includes: a fixed unit that has guide surfaces and coaxial shaft portions; a movable unit that includes an outer surface, a concave portion having side surfaces, guide grooves, and notches; and a lock member that is swingably supported with the fixed unit and interposed between the side surfaces. The lock member has convex portions. The convex portions are slidably fitted to the guide grooves through the notches. Each of the convex portions has end portions. A length of the convex portion between the end portions is larger than an opening width of each of the notches. The end portion is formed thinner than another end portion, so that a gap is formed between the end portion and an inner surface of the guide groove.