Disclosed is an organic piezoelectric material which has excellent piezoelectric characteristics and excellent handling properties. Also disclosed are an ultrasound transducer using the organic piezoelectric material, an ultrasound probe, and an ultrasound medical diagnostic imaging system. Specifically disclosed is an organic piezoelectric material which contains a base material that is formed from a resin, and a specific compound (1) that has at least one linking group selected from among specific linking groups. The organic piezoelectric material is characterized in that the relation shown below is satisfied when the CLogP values of the specific compound (1) and the base material are respectively represented by CLogP(1) and CLogP(base material). Relation: CLogP(1)−CLogP(base material)≦3.0.
