Queues are provided, which are a high-speed small-capacity queue disposed in a high-speed small-capacity medium inputting and outputting online form messages at high speed and a low-speed large-capacity queue disposed in a low-speed large-capacity medium inputting and outputting batch form messages at a speed slower than the high-speed small-capacity medium. A residence rate detection unit detects a residence rate of the form messages in the high-speed small-capacity queue. When the form message is received, a storage control unit stores the form message into the high-speed small-capacity queue or the low-speed large-capacity queue determined based on the priority, the availability of the high-speed small-capacity medium and the residence rate. A dynamic allocation change unit transfers the form messages between the queues based on the residence rate of the high-speed small-capacity queue 30-1 and the availability of the high-speed small-capacity medium.