According to the present invention, a state information collecting device having a microphone, a temperature sensor, and an acceleration sensor capable of detecting a sound, body temperature, and activity of a companion animal is worn on one side of an animal body of an animal, and the information collected by the state information collecting device is analyzed. The present invention relates to a method for detecting an emotional state of a companion animal to transmit the emotional state information of the companion animal to a portable terminal possessed by the animal owner. The emotional state detection method of the companion animal including the main technical idea of the present invention (a) wearing a state information collection device for receiving state information of a companion animal on one side of the body of the companion animal； (b) selecting and inputting a kind of the companion animal through an input unit of the state information collecting device； (c) receiving a sound of the companion animal through a microphone, which is a component of the state information collecting device, on a predetermined time unit； (d) transmitting the kind information of the companion animal and the sound information to the companion animal emotion analysis server using a wireless communication network； (e) extracting feature information of the sound information； (f) selecting predetermined state information corresponding to the kind information of the companion animal and the characteristic information from a database； (g) transmitting the status information to a portable terminal of the companion animal using a wireless communication network, The sound received through the microphone in the step (c) is sampled at a predetermined sampling period in the time domain and then converted into a digital signal and transmitted to the companion animal emotion analysis server of the step (d), The state information may be any one of various emotional states of the companion anim
