A friction spot joining device configured to carry out friction spot joining of a pair of plates includes an advance-retreat drive configured to advance and retreat a tool to/from the plates a rotation drive configured to rotate the tool, and a controller configured to control the advance-retreat drive and the rotation drive. The controller executes a joining control in which the tool is caused to give pressure to the plates while the tool is rotated so that the tool is pushed into the plates, and a separating control in which the tool is separated from the plates when an integrated value (P=ID×ΔT) calculated using a current value (ID) of the rotation drive during the joining control and a driving period of time (ΔT) during the joining control is determined to be reached a target value.