To improve operation efficiency of a trimming device, and to reduce a load of a worker by complicated replacement work.

This cutter replacement device is used for this trimming device. The cutter replacement device includes: a storage part (31) for storing a plurality of cutters (22); a holding part (32) of the cutter (22); a pressing means (33) to press the cutter (22) at the holding part (32); and a slider (34) for transporting the cutter (22) from the storage part (31) to the holding part (32). A planar part (35) is formed on a slider (34), and the cutter (22) is held by the planar part (35) and the pressing means (33). When the slider (34) is retracted from a forward attitude (F), the cutter (22a) is ejected by the gravity. When the slider (34) comes into the forward attitude (F) from a backward attitude (B), the cutter (22b) is held.