Disclosed is a sheet transport device and an image forming apparatus, wherein the sheet transport device includes a main body, a first transport path through which a transported sheet passes, a second transport path through which the sheet that passes through the first transport path and is reversed in a transport direction thereof passes, having a curved portion on a downstream side thereof, a first guiding member that forms a first guiding surface of the second transport path, and a second guiding member that forms a second guiding surface opposite to the guiding surface, wherein the first guiding member is supported to be rotatable between a guiding posture where the sheet is guided and an open posture that rotates from the guiding posture to open the guiding surfaces, and an interval between the first guiding member and the second guiding member in the open posture is greater than that in the guiding posture.