Provided is an observation device with which it is possible, when displaying an image overlaid on an
optical image of a subject, to adjust the
visibility of the image and the
optical image according to the intensity of environmental light. The observation device (30) comprises an optical
system (32), a display mechanism (34) that displays the image on the basis of a
signal generated by an imaging element (20), and a light-blocking mechanism (36) having a variable light-blocking rate. The
optical image has a first optical region (OP1) and a second optical region (OP2). The display mechanism (34) overlays the image on the first optical region (OP1), and displays the image so that a user can observe the image together with the optical image. The light-blocking mechanism (36) is positioned in the light path between the subject and the display mechanism (34) and has a
first light-blocking region (36a) overlapping the first optical region (OP1), and a second light-blocking region (36b) overlapping the second optical region (OP2). A control process is executed on the light-blocking mechanism (36) with a
control unit (40) to control the light-blocking rate of the
first light-blocking region (36a) and the second light-blocking region (36b) on the basis of the intensity of the environmental light.