A biological measuring device includes a light source that emits first light illuminating an area on a living body, an imaging device that detects second light returned from the living body and acquires a first image including at least part of the living body, and a control circuit that controls the light source. If a specific part of the living body is not located in a predetermined coordinate range in the first image, the control circuit restricts emission of the first light from the light source. The predetermined coordinate range is set outside the area.