A lid opening/closing device includes an actuator configured to generate first power for opening a lid, an external force operation mechanism configured to convert an external force into second power for opening the lid, and a power transmission mechanism configured to transmit the first and second power to the lid. The power transmission mechanism includes a first shaft configured to rotate by the first and second power, and a second shaft configured to open/close the lid by the rotation of the first shaft. The external force operation mechanism includes a rotation member. The power transmission mechanism includes an engagement switching portion. The rotation member is integrally incorporated into the power transmission mechanism, and is placed on a side, which is the same as a side on which the first shaft is placed, with respect to the actuator.