A method and apparatus for measuring the 
biological condition of an animal by acquiring and analyzing its biological signals are provided. The biological signals from 
skin temperature, a photoplenthysmogram (PPG), an electrocardiogram (ECG), electrodermal activity (EDA), an electromyogram (EMG), and an electrogastrogram (EGG) are detected using a biological 
signal detection unit which is attached to the animal's 
skin. Feature vectors, including the mean 
heart rate of the photoplenthysmogram and its standard deviation, the 
very low frequency, 
low frequency, and 
high frequency components of 
heart rate variability, the frequency and mean amplitude of 
skin conductance responses, and the mean and maximum skin temperatures, are extracted from the detected biological signals. The 
biological condition, including needs and emotions, of the animal as to whether or not the animal feels hunger or fear, how much the animal is stressed, or whether or not the animal needs to have a bowel movement, is determined using a pattern classifier which has learned reference vectors, which reflect the behaviors, needs, and emotions of different kinds of animals for various biological conditions and are stored in a predetermined 
database. Therefore, the 
biological condition of the animal can be determined through instrumental communication, not through human languages, and the breeding of pets can be efficiently managed.