A secondary transfer device that performs secondary transfer of a toner image onto a paper sheet at a predetermined secondary transfer position, the toner image having been transferred onto an outer peripheral surface of an intermediate transfer belt through primary transfer, the intermediate transfer belt being stretched around a plurality of rollers, the intermediate transfer belt having an endless annular shape and a predetermined width, the secondary transfer device comprising: a pressure releaser that moves a secondary transfer roller between a pressing position for pressing the intermediate transfer belt being nipped between the secondary transfer roller and a counter roller in contact with an inner peripheral surface of the intermediate transfer belt at the secondary transfer position, and a separate position separated from an outer peripheral surface of the intermediate transfer belt; a first driver that drives the pressure releaser; a high-speed pressure reducer that temporarily performs pressure reduction on a nip pressure for the secondary transfer roller at the pressing position to press the intermediate transfer belt being nipped between the secondary transfer roller and the counter roller, when a top edge and a bottom edge of a paper sheet pass through between the secondary transfer roller and the intermediate transfer belt; and a second driver that drives the high-speed pressure reducer, wherein the pressure releaser includes: a pressure cam supported by a rotation shaft that is in the same direction of a shaft of the secondary transfer roller and is driven by the first driver; and a pressure arm that comes into contact with the pressure cam and swings, to move the secondary transfer roller between the pressing position and the separate position, the high-speed pressure reducer includes: a pressure reducing cam supported by a rotation shaft that is in the same direction as the shaft of the secondary transfer roller and is driven by the second driver; and a pressure reducing arm that comes into contact with the pressure reducing cam and swings, to move the secondary transfer roller at the pressing position in such a direction that the nip pressure becomes lower, and a center of an axis of the pressure reducing cam is disposed in a circle having a radius extending from a point of support of the pressure arm to a center of an axis of the pressure cam. a pressure releaser that moves a secondary transfer roller between a pressing position for pressing the intermediate transfer belt being nipped between the secondary transfer roller and a counter roller in contact with an inner peripheral surface of the intermediate transfer belt at the secondary transfer position, and a separate position separated from an outer peripheral surface of the intermediate transfer belt; a first driver that drives the pressure releaser; a high-speed pressure reducer that temporarily performs pressure reduction on a nip pressure for the secondary transfer roller at the pressing position to press the intermediate transfer belt being nipped between the secondary transfer roller and the counter roller, when a top edge and a bottom edge of a paper sheet pass through between the secondary transfer roller and the intermediate transfer belt; and a second driver that drives the high-speed pressure reducer, wherein the pressure releaser includes: a pressure cam supported by a rotation shaft that is in the same direction of a shaft of the secondary transfer roller and is driven by the first driver; and a pressure arm that comes into contact with the pressure cam and swings, to move the secondary transfer roller between the pressing position and the separate position, the high-speed pressure reducer includes: a pressure reducing cam supported by a rotation shaft that is in the same direction as the shaft of the secondary transfer roller and is driven by the second driver; and a pressure reducing arm that comes into contact with the pressure reducing cam and swings, to move the secondary transfer roller at the pressing position in such a direction that the nip pressure becomes lower, and a center of an axis of the pressure reducing cam is disposed in a circle having a radius extending from a point of support of the pressure arm to a center of an axis of the pressure cam.