In a ranging device, a controlling unit alternatively switches orders in time series of a first pulse-transfer-signal and a second pulse-transfer-signal per frame term and outputs the first and second pulse-transfer-signals. Furthermore, an arithmetic unit arithmetizes a distance to an object based on total quantities of charges of signal charges, in two frame term consecutive in the time series, accumulated in a first charge-accumulating region and a second charge-accumulating region in accordance with the first and second pulse-transfer-signals having an identical phase.