A damper opening/closing device installed in an opening used for air conditioning, the damper opening/closing device comprising: an opening/closing lid; a retention mechanism configured to retain the opening/closing lid and place the opening in an open state during a period in which supply of electrical power is being carried out, and to release retention of the opening/closing lid and place the opening in a closed state when the supply of electrical power is stopped; and a return mechanism configured to return the opening/closing lid to the state of being retained by the retention mechanism, in a case that the opening/closing lid is in a closed state during the period in which the supply of electrical power is being carried out; characterized in that the return mechanism includes: a first break contact and a second break contact; a motor configured to be rotationally driven based on at least one of the first break contact and the second break contact being placed in an on state; and an arm configured to rotate in a direction to open the opening/closing lid from an initial position as the motor is rotationally driven, the first break contact is placed in an off state based on an open state of the opening/closing lid, and the second break contact is placed in an off state based on the arm being returned to the initial position; and a crank plate configured to be rotated by driving of the motor, and to rotate the arm in the direction to open the opening/closing lid; and a cam plate configured to be rotated together with the crank plate by driving of the motor, wherein the cam plate includes a cam surface configured to place the second break contact in the off state based on the arm being returned to the initial position. an opening/closing lid; a retention mechanism configured to retain the opening/closing lid and place the opening in an open state during a period in which supply of electrical power is being carried out, and to release retention of the opening/closing lid and place the opening in a closed state when the supply of electrical power is stopped; and a return mechanism configured to return the opening/closing lid to the state of being retained by the retention mechanism, in a case that the opening/closing lid is in a closed state during the period in which the supply of electrical power is being carried out; characterized in that the return mechanism includes: a first break contact and a second break contact; a motor configured to be rotationally driven based on at least one of the first break contact and the second break contact being placed in an on state; and an arm configured to rotate in a direction to open the opening/closing lid from an initial position as the motor is rotationally driven, the first break contact is placed in an off state based on an open state of the opening/closing lid, and the second break contact is placed in an off state based on the arm being returned to the initial position; and a crank plate configured to be rotated by driving of the motor, and to rotate the arm in the direction to open the opening/closing lid; and a cam plate configured to be rotated together with the crank plate by driving of the motor, wherein the cam plate includes a cam surface configured to place the second break contact in the off state based on the arm being returned to the initial position. a first break contact and a second break contact; a motor configured to be rotationally driven based on at least one of the first break contact and the second break contact being placed in an on state; and an arm configured to rotate in a direction to open the opening/closing lid from an initial position as the motor is rotationally driven, the first break contact is placed in an off state based on an open state of the opening/closing lid, and the second break contact is placed in an off state based on the arm being returned to the initial position; and a crank plate configured to be rotated by driving of the motor, and to rotate the arm in the direction to open the opening/closing lid; and a cam plate configured to be rotated together with the crank plate by driving of the motor, wherein the cam plate includes a cam surface configured to place the second break contact in the off state based on the arm being returned to the initial position.