To achieve a simple configuration for determining whether access to a memory provided on a circuit board is made and a circuit board is mounted.

A circuit board 60 is capable of being mounted on a liquid consumption device provided with a body side light-emitting element and a body side light-receiving element. The circuit board 60 includes: a memory 65; a container side light-receiving element 63 for receiving the light emitted from the body side light-emitting element; a mirror element 64 for reflecting the light toward the body side light-receiving element; and a control section 66 configured to extract an input signal out of the light received by the container side light-receiving element 63 and put a memory 65 in operation based on the extracted input signal, and drive the mirror element 64 according to an output signal outputted from the memory 65 to change the reflection direction of the light.