Recent developments of numerical and experimental methods for flow analysis have introduced new concept into design process of fluid machinery. In the basic design of multiblade fan, in which the flow is quite complicated by three-dimensionality and unsteadiness caused by rotating impeller with forward-curved blades and asymmetric housing, numerical and experimental methods are also replacing empirical techniques. Especially PIV method, which has been developed remarkably as a velocity field measurement technique, is powerful tool for the analysis of complicated flows induced in the multiblade fan, and the instantaneous velocity field measured by it can be also used to verify the reliability of numerical results. Recent requirements in the design of the multiblade fan being used in automobile air conditioning units are high pressure at high flow rate, noise reduction and downsizing to realize amenity in the cabin of automobile. In order to meet these requirements, detailed flow analysis throughout the fan must be carried out by using new technology of numerical and experimental method. PIV measurements of the blade passage flow in the impeller of multiblade fan give concrete knowledge for the blade shape design and for the noise analysis.