Provided are apparatus and system for pest detection and a method for detecting pest damage to prevent pest damage in wooden building structures. The apparatus according to one aspect of the present invention comprises: a post-shaped main body extending in a set direction and formed therealong, and comprising a plurality of holes distanced from each other with a wall therebetween, the wall comprising timber which can be despoiled by pest; and a sensor unit allowing attachment and detachment to and from the upper end of the main body. Here, the sensor unit may comprise: a light-emitting unit comprising at least one light-emitting body for irradiating the interior of at least one hole among the plurality of holes; a sensing unit for sensing the light, emitted from the light-emitting unit, in the interior of at least one hole from among the plurality of holes; and a detection unit for outputting a light signal received from the sensing unit as an electrical signal.