A brake cylinder device comprising: a service brake means including a first piston on which a first pressure chamber and a first spring act in opposite directions, the first piston moving in a braking direction by supply of pressure fluid to the first pressure chamber against an elastic force of the first spring; and a spring brake means including a second piston on which a second pressure chamber and a second spring act in opposite directions, the second piston moving in the braking direction by an elastic force of the second spring due to a transition from a state where pressure fluid is supplied to the second pressure chamber to a state where pressure fluid is discharged from the second pressure chamber, both the service brake means and the spring brake means being capable of being operated, wherein the brake cylinder device further comprises: a spindle that is connected to the first piston so as to be rotatable about an axial direction, that penetrates the second piston, and that transmits an elastic force from the spring brake means to the first piston; a first clutch mechanism that includes a first nut member supported rotatably with respect to the second piston and screwed to the spindle, that establishes a connecting state where the spindle and the second piston are connected by movement of the first nut member together with the second piston with respect to the spindle by an elastic force of the second spring, due to a transition from a state where pressure fluid is supplied to the second pressure chamber to a state where pressure fluid is discharged from the second pressure chamber, and that establishes a disconnecting state where the spindle and the second piston are disconnected in a state where pressure fluid is supplied to the second pressure chamber; and a first spindle holding means that restricts a rotatable angle of the spindle with respect to the first piston and that holds the spindle with respect to the first piston in a state where the spindle is urged in a rotation direction that is opposite to a rotation direction of the spindle in which the first nut member is deeply screwed to the spindle. a service brake means including a first piston on which a first pressure chamber and a first spring act in opposite directions, the first piston moving in a braking direction by supply of pressure fluid to the first pressure chamber against an elastic force of the first spring; and a spring brake means including a second piston on which a second pressure chamber and a second spring act in opposite directions, the second piston moving in the braking direction by an elastic force of the second spring due to a transition from a state where pressure fluid is supplied to the second pressure chamber to a state where pressure fluid is discharged from the second pressure chamber, both the service brake means and the spring brake means being capable of being operated, wherein the brake cylinder device further comprises: a spindle that is connected to the first piston so as to be rotatable about an axial direction, that penetrates the second piston, and that transmits an elastic force from the spring brake means to the first piston; a first clutch mechanism that includes a first nut member supported rotatably with respect to the second piston and screwed to the spindle, that establishes a connecting state where the spindle and the second piston are connected by movement of the first nut member together with the second piston with respect to the spindle by an elastic force of the second spring, due to a transition from a state where pressure fluid is supplied to the second pressure chamber to a state where pressure fluid is discharged from the second pressure chamber, and that establishes a disconnecting state where the spindle and the second piston are disconnected in a state where pressure fluid is supplied to the second pressure chamber; and a first spindle holding means that restricts a rotatable angle of the spindle with respect to the first piston and that holds the spindle with respect to the first piston in a state where the spindle is urged in a rotation direction that is opposite to a rotation direction of the spindle in which the first nut member is deeply screwed to the spindle. a spindle that is connected to the first piston so as to be rotatable about an axial direction, that penetrates the second piston, and that transmits an elastic force from the spring brake means to the first piston; a first clutch mechanism that includes a first nut member supported rotatably with respect to the second piston and screwed to the spindle, that establishes a connecting state where the spindle and the second piston are connected by movement of the first nut member together with the second piston with respect to the spindle by an elastic force of the second spring, due to a transition from a state where pressure fluid is supplied to the second pressure chamber to a state where pressure fluid is discharged from the second pressure chamber, and that establishes a disconnecting state where the spindle and the second piston are disconnected in a state where pressure fluid is supplied to the second pressure chamber; and a first spindle holding means that restricts a rotatable angle of the spindle with respect to the first piston and that holds the spindle with respect to the first piston in a state where the spindle is urged in a rotation direction that is opposite to a rotation direction of the spindle in which the first nut member is deeply screwed to the spindle.