An electromagnetic wave detecting device comprising: an emission unit configured to emit electromagnetic waves having coherence; an electromagnetic wave modulating unit configured to modulate one or both of a phase and an amplitude of the emitted electromagnetic waves and to change a state of the modulation relative to an imaging target; and a post-modulation electromagnetic wave intensity detecting unit configured to detect an intensity of post-modulation electromagnetic waves, which are the modulated electromagnetic waves acquired by modulating the electromagnetic waves emitted from the emission unit using the imaging target and the electromagnetic wave modulating unit, using one pixel.