A first storage unit is accessed randomly in a unit equal to or greater than a predetermined data unit. The first storage unit stores a target program required to be read randomly in a unit smaller than the data unit to execute. A second storage unit stores a reading program for reading the target program from the first storage unit. A control unit reads the target program from the first storage unit according to the reading program of the second storage unit. The control unit stores the read target program to a third storage unit that can be accessed in a unit smaller than the data unit. The control unit executes the target program stored in the third storage unit to gain access randomly to the first storage unit in a unit smaller than the data unit in a quasi manner.