An object of the invention is to provide a diversity receiver and a reception system switching method capable of controlling diversity reception start and stop according to the switch condition responsive to person's liking and the use environment.An input section (109) allows the user to select and specify any of a diversity reception mode using two reception channels at all times, a single reception mode using a single reception channel at all times, or an automatic control reception mode for switching between the diversity reception and the single reception in response to the reception state of each mode, and a control section (107) determines a switching determination condition used in the automatic control reception mode according to mode selection information of other two modes. If the diversity reception selection frequency is large, the control section changes the determination condition to a determination condition for increasing the switching frequency to the diversity reception; if the single reception selection frequency is large, the control section changes the determination condition to a determination condition for increasing the switching frequency to the single reception.