The image measurement device includes: a side-emitting illumination device that has a light amount distribution sharply changing in a photographing axis direction of a camera, and irradiates a workpiece on a movable stage with illumination light from a side; a measurement target place specifying part that specifies a measurement target place on a workpiece image; an illumination position adjusting part that moves the side-emitting illumination device in the photographing axis direction, to adjust a relative position of the side-emitting illumination device to the movable stage; a relative position identifying part that obtains a change in luminance in the measurement target place with respect to two or more of the workpiece images photographed by making the relative position different, to identify a relative position; an imaging control part that controls the illumination position adjusting part based on the identified relative position and drives the side-emitting illumination device.