PURPOSE: To provide the exhausting device for sphygmomanometer capable of shifting a control mode in a short time causing less deviation from the target control amount without receiving the effect of pulse wave.

CONSTITUTION: A manchette (cuff) 1, an electromagnetic exhausting valve 4 exhausting the cuff 1, a valve control amount generation device 2 which outputs a signal to control the opening/closing degree of the valve 4, a 1st mode changing the driving control amount in a short time in the initial decompression process till the valve 4 obtains the proper exhaust amount, and a 2nd mode performing the proper exhausting control in order to measure the blood pressure, thereafter, are provided. A controller 9 shifting the mode from the 1st mode to the 2nd mode based on the driving control amount of the valve is installed.