The invention discloses a rotary speed measuring device and a rotary speed measuring method. The rotary speed measuring device is realized by the following steps: a vibration
signal picking sensor is fixedly arranged on a shell of a rotary body to be measured, a supporting seat, a rigid foundation or a rigid object which is in direct contact with the rotary body to be measured and is adjacent to a rotary body; a vibration
signal excited by the rotary body to be measured is acquired by the vibration
signal picking sensor; the vibration signal is transmitted to a signal analyzing and
processing module by a signal transmission lead wire; and the signal analyzing and
processing module is used for analyzing and
processing the vibration signal so as to extract the rotary speed of the rotary body to be measured. The rotary speed measuring method comprises the steps of: setting a sampling frequency, a
data truncation length and a vibration order; carrying out vibration signal picking, filtering, data windowing,
data truncation,
data conversion,
feature data extraction,
feature data check, rotary speed calculation, rotary speed check, vibration order check and rotary speed real-time measurement; and according to the vibration order relation, calculating the rotary speed of the rotary body to be measured. The rotary speed measuring device can measure the rotary speed of the rotary body to be measured without directly contacting with the rotary body to be measured; and the measured rotary body does not need an outward extending end, so that the rotary speed measuring device is convenient to use.