An inter-integrated circuit (I2C) communication device, includes an I2C command transmission unit that transmits an expanded command to an optical module with which the I2C command transmission unit communicates together with software data, the expanded command including a command for transmitting the software data to the optical module and a command for collecting alarm monitor information from the optical module for monitoring the occurrence of an abnormality in the optical module, and an I2C command processing unit that, when the expanded command transmitted from the I2C command transmission unit is received, stores the software data transmitted together with the expanded command in a storage unit of the optical module, reads out the alarm monitor information stored in the storage unit, and transmits the read alarm monitor information to the I2C command transmission unit.