A sheet post-processing apparatus includes a first sensor, a second sensor and a controller. The first sensor detects whether or not a staple for performing a binding processing is prepared in a stapler. The second sensor detects that an amount of the staples held by the stapler has become not more than a prescribed amount. The controller judges whether or not to transfer an operation mode of the sheet post-processing apparatus to a first operation mode to perform the binding processing by the stapler to the sheets to be manually fed, based on a detection result of the second sensor, and judges whether or not to perform the binding processing by the stapler, based on a detection result of the first sensor, after having transferred the operation mode to the first operation mode.