Image forming apparatus with deceleration measuring section

An image forming apparatus including: a first and a second photoconductor groups constituted of one or more photoconductors respectively; a first and a second drive control sections for controlling the drive of the first and second photoconductor groups respectively to rotate the photoconductors thereof, and a deceleration measuring section for measuring respective degrees of deceleration when the first and second photoconductor groups rotate under their own inertias with a drive thereof being stopped, wherein the rotational phases of the first photoconductor group and the second photoconductor group are adjusted to be matched therebetween; and the first and second drive control sections determine a control pattern for decelerating so that a degree of deceleration to be applied at the stage of stopping drive of the first and second photoconductor groups become equal to or slower than the slowest one among the degrees of deceleration being measured.