PROBLEM TO BE SOLVED: To provide a cattle estrus detection system and a device that are more excellent in convenience.SOLUTION: A system for detecting estrus of cattle includes at least a first detection device that detects the estrus of the cattle from roar sounds of the cattle, a second detection device that detects the estrus of the cattle from an amount of activities of the cattle, and final determination means that finally determines the presence or absence of the estrus from determination results of the respective detection devices.
