PURPOSE: To improve pump performance reliably by means of a resinous impeller in a Westco type fuel pump.

CONSTITUTION: A plurality of blade grooves 322 and blade plates 323 are formed alternately on the outer periphery of an impeller 32. A partition wall 321 is arranged between a blade groove 322a and a blade groove 322b. The outer peripheral surface part 3210 of the partition wall 321 is situated more inside than the outer peripheral surface part 3230 of the blade plate 323, and the outer peripheral surface part 3210 is formed so as to have prescribed thickness. When the impeller 32 is rotated, two whirling flows formed along the bottom surfaces 3221 and 3222 become confluent smoothly on the more outside than the outer peripheral surface part 3210, so that a flow empty part can be reduced in a pump flow passage. Deformation and so on caused in molding by means of a molding die can be also reduced due to the thickness of the outer peripheral surface part 3210. Thereby, planes as shown by a spotted pattern among the surfaces of the impeller 32 can be formed only by the molding by means of the molding die, and grinding work is applied to both edge surfaces of the impeller 32 and the outer peripheral surface part 3230 of the blade plate 323.