An anti-picking device for a lock includes a casing, a rotating body, a key guiding seat and a linking member. The casing has a compartment. The rotating body is rotatably received in the compartment and has an actuated member adapted to rotate the rotating body relatively to the casing and an insertion hole axially connecting two end faces of the rotating body. The key guiding seat is received in the compartment and has an arc guiding groove and a receiving hole. The arc guiding groove communicates with the receiving hole, and the receiving hole penetrates through the key guiding seat in the axial direction. The linking member is received in the receiving hole of the key guiding seat and has an engaging part at a first end, while a second end of the linking member extends out of the receiving hole.