An ultrasonic flow measuring apparatus includes a pair of transmission/reception units having respective internally-provided ultrasound transmitting/receiving elements disposed to interpose a pipe body in which a fluid flows and fixing means for fixing the pair of transmission/reception units to the pipe body, such that a flow rate of the fluid is measured by the transmitting/receiving elements alternately transmitting and receiving ultrasonic beams propagating in the pipe body in an oblique direction between the pair of transmission/reception units, wherein the pair of transmission/reception units are made of a synthetic resin as a main material and each has a mounter that comes into contact with an outer surface of the pipe body so as to perform mounting and a transmitter/receiver that includes the transmitting/receiving elements inserted into the mounter and internally provided in the mounter respectively, wherein the mounter has an elongated piece-shaped contact portion coming into contact with the outer surface of the pipe body in a longitudinal direction and a through-hole into which the transmitter/receiver is inserted, and wherein the transmitter/receiver has a plate-shaped surface contact portion which comes into surface contact with the pipe body, and an element fixing portion in which the transmitting/receiving element is installed and is fixed, and which has an end surface that serves as a part of the surface contact portion and comes into surface contact with the pipe body, wherein a force transmitting body being in contact with a part of the mounter is provided at the element fixing portion, characterized in that both ends of the contact portion are raised upward and bent upward as the entire contact portion in the longitudinal direction, the through-hole is provided at a center part of the contact portion, the fixing means for fastening both the ends of the contact portion to the pipe body are disposed on both the ends thereof, and the surface contact portion projects to a side of the pipe body more than the contact portion, wherein, when the pair of the transmission/reception units symmetrically abuts the pipe body on both sides, each transmitter/receiver of the pair of the transmission/reception units is disposed at opposite positions via the pipe body, and fixing of each mounter of the pair of the transmission/reception units to the pipe body is performed by fastening both the ends of each contact portion floated from the outer surface of the pipe body with the fixing means, each mounter is strongly pressed in the vicinity of a center thereof to the pipe body, a strong pressing force generated through the fixing is transmitted to each transmitter/receiver via each force transmitting body, and each surface contact portion is strongly pressed to the pipe body. wherein the pair of transmission/reception units are made of a synthetic resin as a main material and each has a mounter that comes into contact with an outer surface of the pipe body so as to perform mounting and a transmitter/receiver that includes the transmitting/receiving elements inserted into the mounter and internally provided in the mounter respectively, wherein the mounter has an elongated piece-shaped contact portion coming into contact with the outer surface of the pipe body in a longitudinal direction and a through-hole into which the transmitter/receiver is inserted, and wherein the transmitter/receiver has a plate-shaped surface contact portion which comes into surface contact with the pipe body, and an element fixing portion in which the transmitting/receiving element is installed and is fixed, and which has an end surface that serves as a part of the surface contact portion and comes into surface contact with the pipe body, wherein a force transmitting body being in contact with a part of the mounter is provided at the element fixing portion, characterized in that both ends of the contact portion are raised upward and bent upward as the entire contact portion in the longitudinal direction, the through-hole is provided at a center part of the contact portion, the fixing means for fastening both the ends of the contact portion to the pipe body are disposed on both the ends thereof, and the surface contact portion projects to a side of the pipe body more than the contact portion, wherein, when the pair of the transmission/reception units symmetrically abuts the pipe body on both sides, each transmitter/receiver of the pair of the transmission/reception units is disposed at opposite positions via the pipe body, and fixing of each mounter of the pair of the transmission/reception units to the pipe body is performed by fastening both the ends of each contact portion floated from the outer surface of the pipe body with the fixing means, each mounter is strongly pressed in the vicinity of a center thereof to the pipe body, a strong pressing force generated through the fixing is transmitted to each transmitter/receiver via each force transmitting body, and each surface contact portion is strongly pressed to the pipe body.