A storage device includes a tamper-resistant module and a flash memory. In correspondence with a command, a CPU inside the tamper-resistant module judges the security of data received from the outside, then recording the data as follows: High-security and small-capacity data is recorded into a memory inside the tamper-resistant module. High-security and large-capacity data is encrypted, then being recorded into the flash memory. Low-security data is recorded as it is into the flash memory. This recording method permits large-capacity data to be stored while ensuring a security (i.e., a security level) corresponding thereto.