A rasp for shaping a bone is provided. The rasp includes a housing, a driving mechanism, a first gear assembly, two linkage units and two blades. The housing has a channel along a first axis. The driving mechanism has an output gear rotating about the first axis. The first gear assembly rotates about a second axis and is driven by the output gear. The first gear assembly has a first and a second rotation surfaces. A first and a second connection points are respectively located on the first and the second rotation surfaces. The linkage units slidably pass through the channel. The first end of each of the linkage units is pivotally connected to the corresponding connection point, such that the second ends move along the first axis in a reciprocating manner. The blades are respectively and detachably connected to the second ends.