An ultrasound probe includes: an ultrasound input/output unit to output a transmission ultrasound to a test object by a pulse signal and a signal input/output unit to output a reception signal when the ultrasound input/output unit receives a reflected ultrasound from the test object, wherein the ultrasound probe is set so that a difference between maximum and minimum values of a group delay in a transmission/reception frequency band at -20 dB of the ultrasonic probe is equal to or less than 0.15 radian, the group delay being obtained from a phase difference for each frequency between the input pulse signal and the reception signal obtained from the reflected ultrasound of the transmission ultrasound output by the pulse signal, or so that a standard deviation of the group delay in the transmission/reception frequency band at -20 dB of the ultrasonic probe is equal to or less than 0.025.
