A V-belt continuously variable transmission comprising: a fixed sheave fixed to a driving shaft; a movable sheave movable toward or away from the fixed sheave in a direction along an axis of the driving shaft and supported by the driving shaft; a coupling arm (91, 147) supported by the movable sheave through a rolling bearing; and a V-belt wound between the fixed sheave and the movable sheave; the fixed sheave, the movable sheave, the coupling arm (91,147), and the V-belt being stored in a transmission case, the transmission case being formed by fastening a plurality of dividable case members (52, 53, 54) with a plurality of fastening members; the V-belt continuously variable transmission further comprising an actuator unit (82, 146) for causing an output member (81, 145) to move in a direction parallel to the axis of the driving shaft with power from an actuator, the actuator unit (82, 146) being supported by the transmission case slidably in a direction perpendicular to the axis of the driving shaft between an engagement position, wherein the actuator unit (82, 146) is mounted to the transmission case from the outside by engaging the output member (81,145) with the coupling arm (91, 147) so that the movement of the output member (81, 145) can be transmitted to the movable sheave, and a disengagement position, where the actuator unit (82,146) is not mounted to the transmission case and the output member (81, 145) is disengaged from the coupling arm (91, 147); wherein a flat mounting surface for mounting the actuator unit (82, 146) is formed on an outer surface of the transmission case; characterized in that a recessed portion recessed inwardly of the transmission case from the mounting surface is formed to have at an inner end thereof a fastening seat face for a specific fastening member out of the plurality of fastening members, the specific fastening member being disposed at a portion corresponding to the mounting surface; and the whole specific fastening member is disposed inwardly of the transmission case relative to the mounting surface. a fixed sheave fixed to a driving shaft; a movable sheave movable toward or away from the fixed sheave in a direction along an axis of the driving shaft and supported by the driving shaft; a coupling arm (91, 147) supported by the movable sheave through a rolling bearing; and a V-belt wound between the fixed sheave and the movable sheave; the fixed sheave, the movable sheave, the coupling arm (91,147), and the V-belt being stored in a transmission case, the transmission case being formed by fastening a plurality of dividable case members (52, 53, 54) with a plurality of fastening members; the V-belt continuously variable transmission further comprising an actuator unit (82, 146) for causing an output member (81, 145) to move in a direction parallel to the axis of the driving shaft with power from an actuator, the actuator unit (82, 146) being supported by the transmission case slidably in a direction perpendicular to the axis of the driving shaft between an engagement position, wherein the actuator unit (82, 146) is mounted to the transmission case from the outside by engaging the output member (81,145) with the coupling arm (91, 147) so that the movement of the output member (81, 145) can be transmitted to the movable sheave, and a disengagement position, where the actuator unit (82,146) is not mounted to the transmission case and the output member (81, 145) is disengaged from the coupling arm (91, 147); a recessed portion recessed inwardly of the transmission case from the mounting surface is formed to have at an inner end thereof a fastening seat face for a specific fastening member out of the plurality of fastening members, the specific fastening member being disposed at a portion corresponding to the mounting surface; and the whole specific fastening member is disposed inwardly of the transmission case relative to the mounting surface.