A bias circuit sets a value of a bias current using a correction coefficient α=0.5 for a predetermined time period from when a state in which a first capacitor and a second capacitor are not charged, then changes the correction coefficient to α=0.9 which is larger than α=0.5, and sets a value of the bias current obtained by using the correction coefficient α=0.9. The constant current source supplies the light emitting element with the bias current obtained by using the correction coefficient α=0.9 and supplies the bias current with a switching current, and thus an electrostatic latent image is formed.