To provide a light adjusting device having a simple, inexpensive, light, compact, and thin structure, facilitating assembling, and capable of keeping high product accuracy.

A light adjusting device comprises first and second substrates 300, 100 having an opening on at least one of them, a clearance portion 400 regulating a clearance between two substrates, an incident light adjusting means 200 having a shaft member 202 which becomes a rotation center and rotating in a plane surface vertical to an optical axis direction between the two substrates, and a driving means driving the incident light adjusting means 200 by a coil 600 formed separately from a magnet formed on the shaft member 202. The driving means mutually rotates the incident light adjusting means 200 to an opening position and a retracting position retracting from the opening position to adjust the incident light passing through the opening. On the first substrate 300, a guide portion 303 for regulating action different from action in a rotating direction of the shaft member 202 is provided.