Conventionally, flaskless molding machines for producing flaskless sand casting molds have been provided. PTL 1 discloses a die change apparatus for use in a flaskless molding machine. This apparatus comprises a flaskless molding machine capable of being equipped with a first die and a second die capable of producing a flaskless casting mold, and a die carrying-in device and a die carrying-out device which face each other across the flaskless molding machine. The flaskless molding machine includes a first die base having a first mounting base and a second die base having a second mounting base. According to PTL 1, a movable plate having the first die and a movable plate having the second die are simultaneously inserted into a space between the first die base and the second die base. Therefore, there are restrictions on thickness of the first die to be mounted on the first die base and thickness of the second die to be mounted on the second die base. Consequently, a first die and second die having a great thickness cannot be employed. Therefore, there is a limit in increasing casting mold design flexibility.