A transmission comprising: a first planetary gear mechanism; a second planetary gear mechanism including a second sun gear, a plurality of second planetary gears which engage with the second sun gear, and a second carrier which supports the plurality of second planetary gears, the second planetary gear mechanism being arranged to be separated from the first planetary gear mechanism in an axial direction of the first planetary gear mechanism; a housing accommodating the first planetary gear mechanism and the second planetary gear mechanism; a first clutch configured to switch between connection and disconnection of the second carrier and the housing, the first clutch being arranged between the first planetary gear mechanism and the second planetary gear mechanism in the axial direction; a second clutch arranged between the first planetary gear mechanism and the second planetary gear mechanism in the axial direction, the second clutch having an outer diameter which is smaller than an outer diameter of the first clutch; a first piston configured so that, by applying pressure to the first clutch, the first clutch is connected; and a return spring lining up with the first clutch in the axial direction, the return spring being arranged on an outside of the second clutch in the radial direction, the return spring being pressing the first piston so as to separate from the first clutch; and a return spring support section fixed to the housing, wherein the first piston has a first flange section, a second flange section arranged to be separated from the first flange section in the axial direction, and a linking section which links the first flange section and the second flange section, the return spring support section is positioned between the first flange section and the second flange section, the first flange section is positioned between the first clutch and the return spring support section, and the return spring is arranged between the return spring support section and the second flange section. a first planetary gear mechanism; a second planetary gear mechanism including a second sun gear, a plurality of second planetary gears which engage with the second sun gear, and a second carrier which supports the plurality of second planetary gears, the second planetary gear mechanism being arranged to be separated from the first planetary gear mechanism in an axial direction of the first planetary gear mechanism; a housing accommodating the first planetary gear mechanism and the second planetary gear mechanism; a first clutch configured to switch between connection and disconnection of the second carrier and the housing, the first clutch being arranged between the first planetary gear mechanism and the second planetary gear mechanism in the axial direction; a second clutch arranged between the first planetary gear mechanism and the second planetary gear mechanism in the axial direction, the second clutch having an outer diameter which is smaller than an outer diameter of the first clutch; a first piston configured so that, by applying pressure to the first clutch, the first clutch is connected; and a return spring lining up with the first clutch in the axial direction, the return spring being arranged on an outside of the second clutch in the radial direction, the return spring being pressing the first piston so as to separate from the first clutch; and a return spring support section fixed to the housing, wherein the first piston has a first flange section, a second flange section arranged to be separated from the first flange section in the axial direction, and a linking section which links the first flange section and the second flange section, a first flange section, a second flange section arranged to be separated from the first flange section in the axial direction, and a linking section which links the first flange section and the second flange section, the return spring support section is positioned between the first flange section and the second flange section, the first flange section is positioned between the first clutch and the return spring support section, and the return spring is arranged between the return spring support section and the second flange section.