To provide an ultrasonic probe, excellent in the acoustic matching with an organism and having an exterior cap for sufficiently securing the mechanical strength.

The external cap 6 including an ultrasonic vibrator 3 is formed of a material such as polymethyl pentene as a base material satisfying a prescribed visco-elastic property. As a result, the mechanical strength against the outer force such as the impact load, bending stress, etc., to act on the exterior cap for the vibrator can be sufficiently secured while maintaining the excellent acoustic matching with an organism, which polymethyl pentene originally has such as minimization of the multiple reflection which may hinder the ultrasonic diagnosis.