A wiper system control method for controlling a wiper system including a wiper blade that performs a reciprocating wiping operation on a wiping surface, and a raindrop sensor that detects a current amount of rainfall based on water droplets adhering to the wiping surface, wherein the wiper blade comprises a driver's seat side wiper blade arranged on a driver's seat side of a vehicle and a passenger's seat side wiper blade arranged on a passenger's seat side of the vehicle, the wiper system control method comprising driving the driver's seat side wiper blade by a first electric motor and driving the passenger's seat side wiper blade by a second electric motor, the first electric motor being driven and controlled by a first wiper control device and the second electric motor being driven and controlled by a second wiper control device connected to the first wiper control device by a communication line; synchronously controlling the first electric motor by the first wiper control device and the second electric motor by the second wiper control device based on a positional relationship between the driver's seat side wiper blade and the passenger's seat side wiper blade; wherein the wiper system has a low speed activation state in which the wiper blade is activated at low speed, and a high speed activation state in which the driver's seat side wiper blade is activated at speed higher than in the low speed activation state, and when rainfall more than or equal to the predetermined amount is detected by the raindrop sensor, the driver's seat side wiper blade is activated in the high speed activation state within a heavy rain time wiping area narrower than a normal wiping operation range set near a forward field of view of the driver and the passenger's seat side wiper blade is activated over a same wiping area as usual, but is synchronized to not interfere with the driver's seat side wiper blade. a wiper blade that performs a reciprocating wiping operation on a wiping surface, and a raindrop sensor that detects a current amount of rainfall based on water droplets adhering to the wiping surface, wherein the wiper blade comprises a driver's seat side wiper blade arranged on a driver's seat side of a vehicle and a passenger's seat side wiper blade arranged on a passenger's seat side of the vehicle, the wiper system control method comprising driving the driver's seat side wiper blade by a first electric motor and driving the passenger's seat side wiper blade by a second electric motor, the first electric motor being driven and controlled by a first wiper control device and the second electric motor being driven and controlled by a second wiper control device connected to the first wiper control device by a communication line; synchronously controlling the first electric motor by the first wiper control device and the second electric motor by the second wiper control device based on a positional relationship between the driver's seat side wiper blade and the passenger's seat side wiper blade; wherein the wiper system has a low speed activation state in which the wiper blade is activated at low speed, and a high speed activation state in which the driver's seat side wiper blade is activated at speed higher than in the low speed activation state, and when rainfall more than or equal to the predetermined amount is detected by the raindrop sensor, the driver's seat side wiper blade is activated in the high speed activation state within a heavy rain time wiping area narrower than a normal wiping operation range set near a forward field of view of the driver and the passenger's seat side wiper blade is activated over a same wiping area as usual, but is synchronized to not interfere with the driver's seat side wiper blade.