An image formation apparatus including: a toner cartridge storing toner; a developer; a hopper temporarily storing toner supplied from the toner cartridge and supplying the developer with the toner; a magnetic sensor including a magnet and a reed switch that determines whether the magnet is within a detection area thereof, one of which is fixed to a predetermined position, and the other of which is configured to move downwards as a surface level of toner stored in a toner storage of the hopper decreases and thus serves as a surface level detector for detecting the surface level; a lifter configured to periodically lift the surface level detector above the surface level such that the magnet goes out of the detection area; and an ON-edge detector configured to detect ON-edges each indicating a point in time when the magnet has entered the detection area.