An optical communication module includes a control unit, a nonvolatile memory and a volatile memory. The control unit monitors the optical communication module and repeatedly receives log information about a state of a host substrate from the host substrate. The control unit stores the log information in the volatile memory, together with a result of monitoring of the optical communication module. When a hazard signal indicating an abnormality relating to power supply from the host substrate is detected, the control unit writes, in the nonvolatile memory, the result of monitoring of the optical communication module and the log information from the host substrate.