The invention discloses a safely-lockable power supply device. The device comprises a plug main body and a power supply socket main body, wherein the plug main body is connected with a power-using device through a cable, and the plug main body can be plugged into the power supply socket main body which in matched connection with the plug main body; the middle of the top end surface of the plug main body is provided with a plug; a locking through hole which extends along a left-and-right direction is formed in the plug main body; and a connection groove is formed in the bottom surface of the power supply socket main body. According to the whole device, by means of manual operation, the locking and unlocking of the plug main body can be completed, and the energization and de-energization ofa power supply hole can be completed, and therefore, operation is simple and convenient. When the device is used, at first the plug main body is locked, and then, power is supplied for the power-usingdevice; when the device is not used, at first, the power-using device is de-energized, and then, the plug main body is unlocked; and therefore, the use of the device is safer and more stable, electric shock accidents which occur when the plug main body is plugged and pulled out can be avoided. The stability of the power supply of the whole device is high, and the operation of the device is safe and reliable.