To provide a system and a method for detecting livestock estrous time.

The system for detecting livestock estrous time has the following construction and mechanism: A switch sheet 13 is laid under the legs of a livestock 11 reared in a barn and the presence/absence of the livestock's stamping is transmitted to a control unit 18. The control unit functions to total stamping frequency per unit time, compare the result with a standard value, and judge whether the livestock 11 is at an estrous time or not. As an instrument such as a pedometer is not worn on the livestock's legs, misdetection attributable to such an instrument's coming off can be prevented. The switch sheet 13 may be installed vertically on a wall surface.