In a frame transfer method and device by which an address space of a shared buffer can be effectively utilized without a reduction of the space even if an abnormal operation occurs in a management of the shared buffer, after frame data is written in the shared buffer during one monitor cycle when the frame data is to be read without fail from the shared buffer, an address space where the frame data has not been read from the shared buffer is detected during a next monitor cycle, and an address space where not a read but a write of the frame data has been performed at least during the monitor cycle is detected. In the next monitor cycle, the address space is released as a free address of the shared buffer.