A component concentration sensing system includes a first component concentration sensor, a collector and a second component concentration sensor. The first component concentration sensor is provided to a channel through which flows a liquid whose component concentration is to be sensed, and is configured to irradiate the liquid with light and sense the component concentration in the liquid from a degree of light absorption. The collector is arranged to collect the liquid flowing through the channel. The second component concentration sensor is configured to irradiate the liquid collected in the collector with light and sense the component concentration in the liquid from the degree of light absorption.
