A transfer belt transfers a toner image carried on a first main surface to a recording medium. When the transfer belt is pressed by using a lower block provided with a hole and an upper block with pressurization force increased at a prescribed rate and thereafter kept constant, E [-] and t0 are curve-fitted to a function E=α×exp(−t0/τ) defined by a time constant τ [s] with respect to an amount of displacement of the transfer belt and a constant α [-], where E [-] is calculated as (a−b)/b, a [μm] represents a maximum value of an amount of displacement of a measurement region, b [μm] represents an amount of displacement of the measurement region after converged, and t0 [s] represents a time period from start of pressurization until the maximum pressurization force, and time constant τ satisfies a condition of 0.015≤τ≤0.1.