To provide an automatic tuning system, an automatic tuning device and an automatic tuning method for accurately predicting processing performance even when a record size is not fixed.

A schedule for executing a processing request to a data warehouse is acquired. A load to predicted hardware and a load to calculated hardware and an existing hardware resource are integrally analyzed. A predicted response time is calculated. The predicted response time is compared with the requested response time. The difference is calculated. When the difference between the predicted response time and the requested response time exceeds a threshold, the hardware resources satisfying the requested response time are added.