A memory system, which is connected to a host device, includes a memory, a host interface which receives a command and an address, which are output from the host device, and a controller which operates in one of a first mode in which the controller converts the address which is received by the host interface and accesses the memory by using the converted address, and a second mode in which the host device directly accesses the memory by using the address which is received by the host interface, the controller controlling switching between the first mode and second mode in accordance with the command.