An adjustable wrench is disclosed. The adjustable wrench is used for an assembly part. The adjustable wrench includes a frame and an adjustable member. An inner side of the frame has a first rack. The adjustable member has a second rack meshed with the first rack. The adjustable member and the frame are meshed with each other by the first rack and the second rack such that the adjustable member forms a first space inside the frame, wherein the adjustable member adjusts a meshing position of the second rack and the first rack to change the size of the first space; thus, the first space can match assembly parts of different specifications.