An ocular focus device. An ocular lens tube is movably disposed in an ocular housing and includes a positioning groove. An ocular lens set is disposed in the ocular lens tube. A positioning member is connected to the ocular housing and is disposed in the positioning groove. When the ocular lens tube moves with respect to the ocular housing, the ocular lens set performs a focus operation, and the positioning member moves in the positioning groove, limiting a moving range of the ocular lens tube with respect to the ocular housing.