A toner level detector, includes: a toner cartridge storing toner and having one side provided with a light-permeable region; an agitator, which is rotatably disposed in the toner cartridge and agitates the toner; a reflective region disposed on an inner surface on the other side of the toner cartridge; a first cleaner disposed on one side of the agitator; a second cleaner disposed on the other side of the agitator; and a transceiver, which is disposed on a body outside the toner cartridge, and outputs an emitting signal to the reflective region through the light-permeable region, wherein the reflective region reflects the emitting signal to generate a reflective signal received by the transceiver through the reflective region, wherein the first cleaner, which is rotating, intermittently cleans the light-permeable region, which is fixed; and the second cleaner, which is rotating, intermittently cleans the reflective region, which is fixed.