A far-infrared hydrotherapy device has a bath unit, an oxygen supplier, a booster pump, a pressure modulator and an acupressure jet. The bath unit has a tub, an outlet pipe and a heat pump. The tub is for accommodating a liquid. The outlet pipe is connected to the tub to allow the liquid to flowing through. The heat pump is connected to the tub and has a temperature controller. The oxygen supplier is connected to the outlet pipe and provides oxygen to the liquid. The booster pump is connected to the outlet pipe to elevate pressure of the liquid. The pressure modulator is connected to an outlet of the booster pump and has a pressure-equalizing device, a water pressure modulating valve, a pressure-stabilizer and a hose sequentially connected. The acupressure jet is connected to the hose and has an outlet. The far-infrared hydrotherapy device is useful for hydrotherapy.