The interaction between a propeller and a flow field around a full form ship is investigated. A method is presented for the prediction of effective velocity field from measured nominal velocity field, The prediction is made two-dimensionally, with three dimensional correction, by use of modified Huang et al.'s method under the assumption that the effect of vorticity, whose axis is vertical, is dominant for the distortion of velocity distribution due to propeller suction. The agreement between measured and predicted total velocity distribution with propeller is comparatively good. Characteristics of effective velocity field around a full form ship is discussed.