This observation device includes an
image acquisition unit 61, a
wavefront propagation calculation unit 62, and an analysis unit 63. The
image acquisition unit 61 irradiates an
observation object with light of a n-th
irradiation condition among the 1st to N-th
irradiation conditions at time tn and time tn + T, acquires a
complex amplitude image u1,n of light at a focal plane at time tn, and acquires a
complex amplitude image u2,n of light at the focal plane at time (tn + T). The
wavefront propagation calculation unit 62 causes a
wavefront of light represented by
complex amplitude images u1,n (r) and u2,n (r) on the focal plane to propagate to another plane, and obtains complex amplitude images u1,n (r) and u2,n (r) representing the wavefront of light on the other plane at that time by calculation. The analysis unit 63 extracts a temporal variation component of the image of the
observation object on the basis of the complex amplitude images u1,1 to u1,N and u2,1 to u2,N on the focal plane and the other plane, and analyzes the temporal variation component. Thus, an observation device capable of acquiring three-dimensional function information of an
observation object by suppressing an increase in the number of images to be acquired is realized.