A device for measuring adhesion of toner to carrier containing a magnetic component, the toner and the carrier being contained in a two-component developer, includes: a developer holding section including a first magnet for holding the two-component developer by a magnetic force; an airflow supply section for supplying airflow to the two-component developer held by the first magnet; a separated toner detecting section for detecting the number of toner separated from the carrier by the airflow; and an adhesion calculating section for calculating the adhesion of the toner to the carrier or an index of the adhesion, based on wind speed of the airflow and the detected number of the separated toner. Thus, the device can measure the adhesion of the toner to the carrier with high reproducibility and exactness.