PROBLEM TO BE SOLVED: To provide a composite piezoelectric body, an ultrasonic probe, and an ultrasonic image diagnosis apparatus, capable of: satisfactorily performing electric matching with the system side of the apparatus； suppressing unnecessary in-plane resonance other than resonance generated in a thickness direction of the piezoelectric body； suppressing generation of spurious inside a band of ultrasonic waves outputted； and obtaining high sensitivity characteristics in a wide band.SOLUTION: An aspect ratio of a piezoelectric body satisfies inequalities of either (1) to (3) or (4) to (6): 0.5&le；W/H&le；0.65...(1), D/H&ge；W/H...(2), D/H&ge；(13 W/H)/3-13/6...(3) 0.5&le；D/H&le；0.65...(4), D/H&le；W/H...(5), W/H&ge；(13D/H)/3-13/6...(6), where H denotes thickness of the piezoelectric body； W denotes length of one side which in a direction perpendicular to a thickness direction； and D denotes length of one side in a direction perpendicular to the thickness direction and to the W direction.
