An object of the present invention is to provide a technique to improve the data transmission efficiency which allows correct reception of the data at the same time. A removable memory device that transmits/receives data to and from a host terminal, which includes: a clock reception section that receives a transmission/reception clock, which is used for transmitting/receiving data between the host terminal and the removable memory device, from the host terminal; a phase synchronization pattern generation section that generates a phase synchronization pattern, which is for adjusting a phase of internal reception clock which the host terminal incorporates for receiving data from the removable memory device, based on the transmission/reception clock; and a transmission section that transmits the generated phase synchronization pattern to the host terminal, and in which the phase synchronization pattern includes a first level signal which lasts for at least two cycles, and a second level signal which follows the first level signal and lasts for one cycle, is provided.