To provide an adjusting method of water discharging rate of a faucet enabling easy and efficient adjustment of water discharging rate wherein measurement and adjustment of the water discharging rate of the faucet apparatus can be conducted at the same time and an open type flowmeter used for the method.

In the adjusting method of water discharging rate of the faucet, the open type flowmeter with graduation of drain flow rate per unit of time at a drainage port is provided below a faucet port. While water is discharged from the faucet port to a container by operating a water shut off valve provided immediately near an upstream side of the faucet port with the faucet port open, the water shut off valve is adjusted so that water level in the container is maintained at an intended graduation position of the open type flowmeter.