A sheet transport device and an image forming apparatus that includes the sheet transport device. The sheet transport device includes a reverse-transport roller, at least one roller guide, and a shaft. The reverse-transport roller is provided to a diverging point of a sheet reversing portion from which a recording medium enters or exits and is configured to transport the recording medium to the sheet reversing portion. At least one roller guide is provided in a vicinity of an end face of at least one side of the reverse-transport roller and is configured to prevent the reverse-transport roller from contacting the recording medium when reversing the recording medium. The reverse-transport roller and the roller guide are disposed on the shaft. Friction of a peripheral surface of the roller guide is configured to be substantially less than that of the recording medium.