To provide a device for automatically repelling a small harmful animal, repelling the small harmful animal exemplified by a rat and invading into the interior of a house such as a kitchen by imparting stress by utilizing a plurality of threatening means.

A housing 2 of the device 1 for automatically repelling the small harmful animal has a small harmful animal sensor 3 sensing the approach of the small harmful animal, a light-emitting part 4 for emitting light by using a sensed signal sent from the small harmful animal sensor 3 as a trigger, one or more arms 6 carrying out reciprocating motion by driving means by using the sensed signal as the trigger, and paddles 5 installed in the tip parts of the arms 6, and striking blows to an installation face. The device 1 exhibits the repelling effects by imparting fear and stress to the small harmful animal by the combination of four kinds of repelling means of the flicker of the light-emitting part 4, the sound and vibration caused when the paddles 5 beat the installation face, and the motion of the arms 6 and paddles 5.