A precision confirmation apparatus (60) in which connection of a connection plug (92) to the connector (6) of a hemadynamometer communicates an air system with the measurement air system (23) of a main body (2) and makes a CPU (80) communicable with the CPU (50) of the hemadynamometer through a communication line (70). Detecting the operation of a precision confirmation mode switch and setting anoperation mode to a precision confirmation mode, the CPU (50) executes blood pressure measurement processing. At this time, the CPU (80) of the precision confirmation apparatus (60) controls respective parts to generate pseudo pulse waves within an air tube (90) and comes into a reception standby state of a maximal blood pressure value from the CPU (50). When receiving the maximal blood pressure value from the CPU (50), the CPU (80) calculates the pressure deviation between the maximal blood pressure value obtained by the hemadynamometer and the maximal blood pressure value obtained by the precision confirmation apparatus(60). When the calculated pressure deviation is not larger than a predetermined threshold, the CPU (80) judges that the measurement precision of the hemadynamometer satisfies a predetermined level and is normal.