An environmental-state determination apparatus includes a pair of detection electrodes which provide therebetween a capacitance which changes in accordance with a state of a surrounding environment, for example, the level of a liquid. A detection signal is input to a signal passage connected to the detection electrodes. A first capacitance parameter representing the capacitance of the detection electrodes is detected on the basis of a signal output from the signal passage in the connected state. The detection signal is input to the signal passage from which the detection electrodes are disconnected. A second capacitance parameter representing the capacitance of the signal passage is detected on the basis of a signal output from the signal passage in the disconnected state. The first capacitance parameter is corrected by subtracting therefrom the second capacitance parameter. The state of the surrounding environment is determined on the basis of the corrected first capacitance parameter.