A flashlight with power supply adapter comprising a front light housing with a light bulb in the tip of the main body of the flashlight. There is a compartment in the main body for storing a rechargeable battery and a spare battery. There are also an on/off switch and a battery select switch for selecting between the rechargeable battery and the spare battery. During use, when the power of the rechargeable battery is drained, the flashlight can still be made to work by changing the battery select switch to the spare battery. As a result, the flashlight is still powered even after the main battery is used.