A guarantee value setting unit stores therein a guarantee value of data send/receive performance with respect to a predetermined volume in a plurality of volumes held by a storage device. A bandwidth management unit calculates an interim target value on the basis of a comparison result between the guarantee value and an actual measurement value of the data send/receive performance with respect to the predetermined volume, allocates, on the basis of the interim target value, a bandwidth that compensates a difference between the guarantee value and the actual measurement value with respect to the predetermined storage area, and determines band distribution with respect to each of the volumes, and instructs the storage device to adjust the bandwidth in accordance with the determined band distribution.