Analog to digital conversion means, and the illuminance sensor device includes an illuminance sensor device electronics

Comprising: analog to digital converter (ADC1, ADC2); reference current Iref1 outputted used as a reference charge amount, Iref2 reference current source (11); switching the reference current Iref1 switch (SW21 is) from the reference current source (11); switching the reference current Iref2 switch (SW22 is) from the reference current source (11); and a control switch (SW21, SW22) a switching control circuit (12). By using the switching control circuit (12) controls the switch (SW21, SW22), 1/2 of the time period for each analog to digital conversion of each analog to digital converter circuit Change (ADC1, ADC2) for use in the reference current Iref1, Iref2. Can be reduced thereby providing a plurality of analog to digital conversion means error between the analog to digital conversion circuit.