an image forming apparatus comprising a photosensitive body , a charger configured to charge the photosensitive body , an exposure unit configured to expose the photosensitive body charged by the charger , a developer transport section configured to cause relative movement with respect to the photosensitive body for transporting developer therebetween , a current measurement section configured to measure a current flowing between the photosensitive body and the developer transport section , and a determination unit configured to compare a current with a threshold , the current measured by the current measurement section when the photosensitive body and the developer transport section move relatively to each other and a first area of the photosensitive body that needs to be exposed faces the developer transport section , and determine whether an exposure of the photosensitive body is proper based on a result of the comparison .