A grinder for grinding an end face of a fiber includes a housing, a fiber fixing module, a base, a transmission shaft, and a grinding pad. The housing includes an annular rack wheel with an internal engaging teeth. The fiber fixing module is positioned on a top of the housing. The base is positioned at a bottom of the housing and includes an eccentric connection portion. An end of the transmission shaft is connected to the connection portion. The transmission shaft is sleeved with an annular pinion having external engaging teeth engaging with the internal engaging teeth. The grinding pad is connected to another end of the transmission shaft and revolves around the rotation axis of the base and rotates around its own rotation axis together with the transmission shaft and matches an end face of a to-be-ground fiber penetrating the fiber fixing module.