To provide a robust liquid flow-meter calibration device that has high calibration accuracy, short calibration period, low running cost, and a simple structure.

The liquid flow-meter calibration device comprises one or more nozzles 10c for discharging test liquid as a jet, a weighing tank 60b capable of taking in the test liquid, a weighing gauge 61b capable of measuring the weight of the weighing tank, a bypass line 20d for discharging the test liquid when the test liquid is not taken into the weighing tank side, and a flow channel switching device 30 for switching between guide of the jet flow to the bypass line and guide of it to the weighing tank. The flow channel switching device is formed of a rotation shaft 53 parallel to the flow direction of the jet, two commutation blades 31 fixed to the rotation shaft and extending in the flow direction of the jet, a flow channel 11c to the weighing tank positioned on one side of the two commutation blades, and a by-pass side straightening plate 21 for guiding the other side of the two commutation blades to the bypass line.