The flow rate meter based on the Laser Doppler Anemometer (LDA) has been developed to evaluate the fuel injection rate. The flow rate meter is called as LDA flow rate meter. The instantaneous flow rate has been measured at the upstream of an injector. The measured results of instantaneous flow rate are influenced by reflection pressure waves from the end of pipe. The effects of the pressure waves appear as undesirable oscillations in the results of the instantaneous flow rate. A reducing method of the oscillations is proposed as data correction. Corrected data of LDA flow rate meter have similar profiles to the results by the BOSCH-Type injection indicator. The results indicate the instantaneous injection rate can be evaluated by using the LDA flow rate meter.