Colour image forming apparatus

An intermediate image transfer type of image forming apparatus of the present invention includes an image carrier (40), an intermediate image transfer body (10), primary image transferring means (62) for transferring a toner image from the image carrier (40) to the intermediate image transfer body (10), and secondary image transferring means (22) for transferring the toner image from the intermediate image transfer body (10) to a sheet. When the surface resistivity of the intermediate image transfer body (10) is measured by a method that repeatedly applies a voltage of 200 V for 60 seconds to the intermediate image transfer body (10) and grounds the intermediate image transfer body (10) for 10 seconds 1,000 consecutive times, a difference in absolute value between the logarithm of the first time of measurement and that of the thousandth time of measurement is 0.5 log OMEGA / &squ& or below.