Provided are an ultrasonic probe and ultrasonic diagnostic apparatus in which the surface temperature of the ultrasonic probe can be kept in a safe range without a reduction in performance. An ultrasonic probe of an embodiment comprises a case, a vibrator, electrical circuitry, and a heat transfer structure. The vibrator is arranged at one end of the case, and transmits ultrasound based on a delay time. The electrical circuitry is accommodated in the case and has a delay circuit for setting the delay time and a pulser for outputting to the vibrator a pulse generated on the basis of the delay time. The heat transfer structure has a member having low thermal conductivity that is disposed between both the electrical circuitry and the case and/or between both the electrical circuitry and the vibrator when the electrical circuitry is energized, whereby heat is transferred from the electrical circuitry to the other end of the case.