An image forming apparatus includes a development section, a toner replenishment section, a toner sensor, and a determination section. The new toner container is filled with first and second toners that have different magnetic characteristics. The new container supplies the first toner to the toner replenishment section prior to the second toner. The determination section determines replacement of an existing toner container by a new one upon the output value of the toner sensor changing from a value out of a first-toner output value range to a value therewithin. The first-toner output value range is a range of an output value of the toner sensor in response to the magnetic characteristic of the first tone.