In an embroidery sewing machine, an embroidery frame support device (7) for supporting a front end portion of an embroidery frame (6) installed in a cantilevered manner includes: a base member (11) that is a base for attaching the embroidery frame support device (7) to the embroidery sewing machine, and a Y slide rail (12) (support member) having a movable end that can move relatively with the base member (11). The embroidery frame support device (7) supports a front end portion of the embroidery frame (6) from a lower surface thereof through an X slide rail (15) attached to a tip portion of the Y slide rail (12). The embroidery frame support device (7) can be attached to the embroidery sewing machine by screwing a base member (11) to a cylinder bed (3). The screwing of the base member (11) to the cylinder bed (3) can be carried out from the upper side of a sewing machine table (1).