In an interrupt control method of a multicore processor system including cores, a cache coherency mechanism, and a device, a first core detecting an interrupt signal from the device writes into an area prescribing an interrupt flag in the cache memory of the first core, first data indicating detection of the interrupt signal, and notifies the other cores of an execution request for interrupt processing corresponding to the interrupt signal, consequent to the cache coherency mechanism establishing coherency among at least cache memories of the other cores when the first data is written; and a second core different from the first core, maintaining the first data written as the interrupt flag, and notified of the execution request executes the interrupt processing, and writes over the area prescribing the interrupt flag written in the cache memory of the second core, with second data indicating no-detection of the interrupt signal.