A separating device for separating workpieces includes a driving unit, a supporting board, and a moving assembly. The supporting board defines a number of sliding grooves spaced from each other. The moving assembly includes a sliding board slidably assembled to the supporting board, and a plurality of first moving blocks for holding workpieces. The sliding board slides along a first direction and defines two latching holes, each extending along a second direction perpendicular to the first direction. Each of the first moving blocks extends through the latching holes to be inserted in one of the sliding grooves. The driving unit drives the sliding board to slide along the first direction. The sliding board forces the number of first moving blocks to slide along the number of sliding grooves.