A fluid measuring device in which an ultrasonic probe provided on an outer pipeline surface transmits and receives ultrasonic waves to and from fluid in a pipeline to measure characteristics of the fluid on the basis of propagation time of the ultrasonic waves, features a wedge included in the ultrasonic probe and having an ultrasonic vibrator provided on a wedge surface. The ultrasonic vibrator may be horizontal to a surface contacting the pipeline so that ultrasonic waves enter the fluid vertically. The ultrasonic vibrator may be provided on a wedge surface inclined with respect to an axial direction of the pipeline so that ultrasonic waves enter the fluid obliquely. The fluid measuring device embodiments are capable of measuring fluid characteristics, such as the type and velocity of various fluids, easily and accurately even when it is difficult to allow an ultrasonic signal to pass through the fluid in a pipeline.