Sheet conveyance device that can detect sheet size

A sheet conveyance device is capable of detecting a sheet length in a conveyance direction correctly, and of detecting a length of a non-standard size sheet correctly. A detection unit detects front and rear ends of a sheet conveyed with a conveyance unit. A measurement unit measures sheet length in a conveyance direction based on a detection result of the detection unit. An acquisition unit acquires a reference length of the sheet. A computation unit computes a correction value that is used to correct a length measured by the measurement unit based on length measured and the reference length acquired in a correction mode. A storage unit stores the correction value computed. A determination unit determines sheet length corrected based on the correction value and the length measured at the time of conveyance of a sheet in a mode other than correction mode.