An optical device comprises: a transmittance changing unit that is provided in front of an eye of a user, and changes transmittance for light from the outside according to a voltage being applied; and a voltage control unit that controls a voltage to be applied to the transmittance changing unit by switching cyclically between a high voltage and a low voltage, wherein the voltage control unit switches the voltage at a cycle that is shorter than the sum of time required for transmittance of the transmittance changing unit to stabilize when changing from a minimum value to a maximum value by switching a voltage and time required for transmittance of the transmittance changing unit to stabilize when changing from a maximum value to a minimum value by switching a voltage.