An ultrasonic probe comprising: a rear block; a rear acoustic matching layer formed on an upper side of the rear block; a piezoelectric ceramic which is formed on an upper side of the rear acoustic matching layer and is configured to propagate a first ultrasonic wave forward and propagate a second ultrasonic wave backward; a front acoustic matching layer formed on an upper side of the piezoelectric ceramic; an acoustic lens formed on an upper side of the front acoustic matching layer; a flexible printed circuit board which is formed between the rear acoustic matching layer and the piezoelectric ceramic and is electrically connected to the piezoelectric ceramic, and a ground plate which is formed between the front acoustic matching layer and the piezoelectric ceramic and is joined to ground patterns of the flexible printed circuit board, characterized in that both ends of the flexible printed circuit board, which are withdrawn from the piezoelectric ceramic, are connected to each other beneath the rear block; wherein the rear acoustic matching layer includes a first rear acoustic matching layer, which is formed on a lower side of the piezoelectric ceramic, and is configured to generate a third ultrasonic wave by reflecting the second ultrasonic wave toward the front of the piezoelectric ceramic and changes the acoustic impedance of the third ultrasonic wave so that the third ultrasonic wave is acoustically matched to the first ultrasonic wave, and a second rear acoustic matching layer, which is formed between the first rear acoustic matching layer and the rear block, and is configured to generate a fourth ultrasonic wave by reflecting the second ultrasonic wave passing through the first rear acoustic matching layer and changes the acoustic impedance of the fourth ultrasonic wave so that the fourth ultrasonic wave is acoustically matched to the first ultrasonic wave, and wherein the front acoustic matching layer includes a first front acoustic matching layer, which is formed on an upper side of the piezoelectric ceramic, and a second front acoustic matching layer, which is formed between the first front acoustic matching layer and the acoustic lens, and performs an acoustic matching for the first, second, third, and fourth ultrasonic waves. a rear block; a rear acoustic matching layer formed on an upper side of the rear block; a piezoelectric ceramic which is formed on an upper side of the rear acoustic matching layer and is configured to propagate a first ultrasonic wave forward and propagate a second ultrasonic wave backward; a front acoustic matching layer formed on an upper side of the piezoelectric ceramic; an acoustic lens formed on an upper side of the front acoustic matching layer; a flexible printed circuit board which is formed between the rear acoustic matching layer and the piezoelectric ceramic and is electrically connected to the piezoelectric ceramic, and a ground plate which is formed between the front acoustic matching layer and the piezoelectric ceramic and is joined to ground patterns of the flexible printed circuit board, characterized in that both ends of the flexible printed circuit board, which are withdrawn from the piezoelectric ceramic, are connected to each other beneath the rear block; wherein the rear acoustic matching layer includes a first rear acoustic matching layer, which is formed on a lower side of the piezoelectric ceramic, and is configured to generate a third ultrasonic wave by reflecting the second ultrasonic wave toward the front of the piezoelectric ceramic and changes the acoustic impedance of the third ultrasonic wave so that the third ultrasonic wave is acoustically matched to the first ultrasonic wave, and a second rear acoustic matching layer, which is formed between the first rear acoustic matching layer and the rear block, and is configured to generate a fourth ultrasonic wave by reflecting the second ultrasonic wave passing through the first rear acoustic matching layer and changes the acoustic impedance of the fourth ultrasonic wave so that the fourth ultrasonic wave is acoustically matched to the first ultrasonic wave, and wherein the front acoustic matching layer includes a first front acoustic matching layer, which is formed on an upper side of the piezoelectric ceramic, and a second front acoustic matching layer, which is formed between the first front acoustic matching layer and the acoustic lens, and performs an acoustic matching for the first, second, third, and fourth ultrasonic waves.