a stream processor that accesses a memory includes : stream processing sections each configured to extract a time stamp in an associated one of input streams , obtain priority information on access to the memory based on a difference between the time stamp and a reference time , output an access request to the memory and the priority information , and , when receiving access permission , access the memory ; and an access controller configured to grant access permission to the stream processing sections repeatedly based on the access request and the priority information in such a manner that the access controller grants access permission to one of the stream processing sections having a highest priority and then , after termination of processing of the stream processing section to which the access permission has been granted , grants access permission to one of the stream processing sections having a next highest priority .