1. A sheet conveyance unit being connected to a sheet discharge unit which discharge a sheet,the sheet conveyance unit comprising:
a sheet inlet port which is connected to a discharge guide provided in the sheet discharge unit;
an inlet guide which is disposed at the sheet inlet port and has an upper guide facing an upper surface of the sheet and a lower guide disposed below the upper guide so as to face a lower surface of the sheet;
a conveyance member which conveys the sheet conveyed into the sheet conveyance unit along the inlet guide; and
a guide switching mechanism which switches the inlet guide between a conveyance position at which the upper guide and the lower guide face each other with a first distance and a separation position at which the upper guide and the lower guide are spaced from each other with a second distance greater than the first distance,
to connect the sheet conveyance unit to the sheet discharge unit,
the inlet guide is disposed to the separation position by the guide switching mechanism before the discharge guide is inserted between the upper guide and the lower guide, and is disposed to the conveyance position after the discharge guide is inserted between the upper guide and the lower guide.