A compression depth calculation system to calculate a compression depth as a magnitude of a depression of a compressed object generated by compression, comprising: a measuring apparatus (1, 1a) to be mounted on the object, and a compression depth calculation apparatus configured to calculate the compression depth on the basis of information from the measuring apparatus (1, 1a), wherein the measuring apparatus (1, 1a) includes: an acceleration sensor configured to detect an acceleration of a movement of a compressed portion of the object; and a magnetic sensor or a pressure sensor configured to output information according to the magnitude of compression with respect to the compressed portion of the object, characterized in that the compression depth calculation apparatus includes: a memory unit configured to memorize information, a second-order differential waveform creating unit configured to create a second-order differential waveform as a waveform of an acceleration of the movement of the compressed portion by performing second-order differential on the information acquired from the magnetic sensor or the pressure sensor; a waveform comparing unit configured to compare the created second-order differential waveform and an acceleration waveform on the basis of acceleration information acquired from the acceleration sensor to output a result of comparison; and a calculating unit configured to calculate a ratio of the acceleration waveform on the basis of the acceleration information with respect to the created second-order differential waveform as a coefficient of transformation on the basis of the output result of comparison; create a displacement waveform as a waveform of displacement of the movement of the compressed portion by multiplying the acquired information from the magnetic sensor or the pressure sensor by the calculated coefficient of transformation; and calculate the compression depth on the basis of the created displacement waveform. a measuring apparatus (1, 1a) to be mounted on the object, and a compression depth calculation apparatus configured to calculate the compression depth on the basis of information from the measuring apparatus (1, 1a), wherein the measuring apparatus (1, 1a) includes: an acceleration sensor configured to detect an acceleration of a movement of a compressed portion of the object; and a magnetic sensor or a pressure sensor configured to output information according to the magnitude of compression with respect to the compressed portion of the object, characterized in that an acceleration sensor configured to detect an acceleration of a movement of a compressed portion of the object; and a magnetic sensor or a pressure sensor configured to output information according to the magnitude of compression with respect to the compressed portion of the object, the compression depth calculation apparatus includes: a memory unit configured to memorize information, a second-order differential waveform creating unit configured to create a second-order differential waveform as a waveform of an acceleration of the movement of the compressed portion by performing second-order differential on the information acquired from the magnetic sensor or the pressure sensor; a waveform comparing unit configured to compare the created second-order differential waveform and an acceleration waveform on the basis of acceleration information acquired from the acceleration sensor to output a result of comparison; and a calculating unit configured to calculate a ratio of the acceleration waveform on the basis of the acceleration information with respect to the created second-order differential waveform as a coefficient of transformation on the basis of the output result of comparison; create a displacement waveform as a waveform of displacement of the movement of the compressed portion by multiplying the acquired information from the magnetic sensor or the pressure sensor by the calculated coefficient of transformation; and calculate the compression depth on the basis of the created displacement waveform. a memory unit configured to memorize information, a second-order differential waveform creating unit configured to create a second-order differential waveform as a waveform of an acceleration of the movement of the compressed portion by performing second-order differential on the information acquired from the magnetic sensor or the pressure sensor; a waveform comparing unit configured to compare the created second-order differential waveform and an acceleration waveform on the basis of acceleration information acquired from the acceleration sensor to output a result of comparison; and a calculating unit configured to calculate a ratio of the acceleration waveform on the basis of the acceleration information with respect to the created second-order differential waveform as a coefficient of transformation on the basis of the output result of comparison; create a displacement waveform as a waveform of displacement of the movement of the compressed portion by multiplying the acquired information from the magnetic sensor or the pressure sensor by the calculated coefficient of transformation; and calculate the compression depth on the basis of the created displacement waveform.