This indoor pest repellant device 10 is provided with: a light source 11； a light concentrating part (the first light concentrating part 13) which concentrates a portion of diffused light LS emitted from the light source 11； and a first displacement unit (the rotation mechanism 14) which changes the relative position of the first light concentrating part 13 relative to the light source 11, and which displaces the irradiation region (the light irradiation region SP1) of the light from the first light concentrating part 13, said irradiation region being formed on a floor. The light concentrating part is provided with a convex lens.
