A raindrop detection apparatus has an amplifier circuit, including a plurality of resistors and resistor selection switches. The control circuit performs the first adjustment to an output of the amplifier circuit, roughly adjusting the output to a target value. The first adjustment is made by selecting one of or a combination of resistors. The control circuit then performs the second adjustment to the output, closely adjusting the output to the target value. The second adjustment is made by adjusting a driving instruction signal, which actually adjusts a light emitting device driving current. These adjustments are performed after an IG switch and an AUTO mode switch of a wiper switch are turned on.