A dehydration device removes moisture from a process gas compressed by a compressor, and includes a contactor that causes a dehydration solvent to absorb the moisture, a still column that separates the moisture from the dehydration solvent, a carrying line that carries the dehydration solvent from the contactor to the still column, a dehydration solvent conveying pump, a bypass line that couples the carrying lines upstream and downstream of the dehydration solvent conveying pump, a first on-off valve disposed in the bypass line, and a control device. In a case where the pressure detected by a pressure sensor is lower than a first predetermined pressure, the control device closes the first on-off valve and causes the conveying pump to operate, whereas in a case where the pressure detected by the pressure sensor is equal to or higher than the first predetermined pressure, the control device opens the first on-off valve and causes the conveying pump to stop.