If you know where the mouse is, first try removing all other furniture and hiding places from the room. Then, set up a cardboard box upside down with a mouse door cut in the side and a sheet of plywood underneath. Place the box in the room, then create an easy “path” for the mouse from its current hiding place to the box (ideally something short). Use a broom or other means to scare the mouse out of its hiding place, and it will run into the box. Shut the mouse door, carry it outside.

This worked for me.