Disclosed is a pluggable power supply device. When a pluggable plug is to be in combination with a power supply seat, an insertion portion is first inserted in an accommodation portion of the power supply seat, allowing a second engagement portion to be engaged with a first engagement portion, and causing the gripping device on the power supply seat to be translated horizontally; a sliding block is then moved horizontally to a separation position and drive a first gripping portion on one side of thereof, allowing a second gripping portion to enter the accommodation portion. Thereafter, an elastic element drives the sliding block to translate horizontally to a gripping position, thereby moving the first gripping portion to be engaged with the second gripping portion. When the pluggable plug is to be removed, it can be taken out only by moving the sliding block horizontally.