The discharge characteristics of orifice or nozzle for high-pressure type air-micrometer were investigated for pressure difference from 0.2kg/cm2 to 3.0kg/cm2 over a range of pressure ratio from 0.25 to 0.95. The experiment has revealed the following : 1. By plotting cε (c : discharge coefficient of incompressible fluid, ε : expansion factor) against the pressure ratio, using parameter l/d, a nearly linear relation was obtained. For rounded nozzle, cylindrical nozzle and knife-edged orifice, a change of flow regime occurs respectively at the pressure ratio of 0.53, 0.55, and 0.63. 2. The values of ε at a position where the pressure ratio equal 1 agree with discharge coefficients of incompressible fluid over so-called "limit of constancy" of Reynolds number. 3. Discharge coefficients of each type of nozzle and orifice were collected and one experimental formula was worked out for each. 4. Downstream pressure and temperature are recovered at a position respectively 5 times and 4 times the pipe diameter. 5. Recovery rate of pressure was nearly same as in 1st report.