This study estimated the accuracy of an X-ray analyzer by comparing it with an ionization chamber and a tube voltage current meter, and investigated whether it was usable as a substitute for a reference meter for output measurements for quality control purposes. The X-ray output analyzer used was a Piranha (RTI Electronics), a non-invasive instrument. The two subjects of measurements were as follows: the tube voltage, exposure, and half-value layer used in ordinary X-ray radiographic system equipment, and the exposure and half-value layer in X-ray equipment for mammographic systems. The results for a conventional radiographic system showed the error rates for tube voltage, exposure, and half value layer to be within ±1.0%, ±1.8%, and ±4.3%, respectively. The Piranha is not influenced by the dependence of the beam quality in a range of the tube voltage in clinical use. In X-ray equipment for mammographic system results, error rates for exposure and half value layer were ±2.2% and within ±4.0%, respectively. We conclude that it is possible to use the Piranha as an alternative reference meter for quality control of X-ray equipment for typical radiographic and mammographic systems.