PROBLEM TO BE SOLVED: To provide an ultrasonic wave probe and an ultrasonic diagnostic device, for quickly reducing weight of the ultrasonic probe itself and weight of a cable (a bundle of signal lines) which electrically connects the ultrasonic probe and a body while maintaining high detection precision.SOLUTION: An object to be connected of a part of a delay circuit 24 of respective delay circuits 24 provided on an ultrasonic probe 2 is switched between a second electric-acoustic conversion layer 15 and a first electric-acoustic conversion layer 11 by a switch circuit 25. The part of the delay circuit 24 is used for both receiving an electric signal outputted from each of piezoelectric elements 151 of sub-arrays set to the second electric-acoustic conversion layer 15 and receiving an electric signal outputted from each of the piezoelectric elements 111 of sub-arrays set to the first electric-acoustic conversion layer 11.
