To provide a low-cost optical modulating device which has a simple structure optically modulating incident light by changing its reflecting direction, has quick response, imposes no restriction on the wavelength of the incident light in use, stably and reliably operates with a low driving voltage, and requires a small number of manufacturing processes.

This optical modulating device is equipped with a thin-film both-end fixed beam 2 which is constituted by combining a reflecting means 1 with the side face thereof and formed of a thin film and has both the ends fixed and deforms with an electrostatic force, a substrate electrode 3 which faces the thin-film both-end fixed beam 2 and applies the driving voltage, a substrate 4 which holds the held parts 2a of both the ends of the thin-film both-end fixed beam 2 while forming the substrate electrode 3 in the recessed shape part of the substrate 4, and a displacement accelerating means 5 which is so formed that the end side of one held part 2a1 of the beam 2 held by the substrate 4 is easier to displace than the end side of the other held part 2a2.