1. An abdominal respiration training system comprising: a sensor which is attached to an abdominal region of a person to be examined and detects the motion of the abdominal wall by an abdominal respiration; a training pattern generating means for generating an ideal pattern of an inspiration time and/or an expiration time on the basis of ideal values of a respiration ratio, a respiration depth, and a number of respiration times, so as to obtain a relaxation state in which an alpha wave mainly appears; a breath pattern calculating means for calculating an actual breath pattern of the person to be examined from a detection signal of said sensor; a comparison deciding means for comparing the pattern calculated by said breath pattern calculating means with the ideal breath training pattern from said training pattern generating means, and for deciding a degree of similarity between said calculated pattern and said ideal breath training pattern; and an informing means for informing said ideal breath training pattern and an output of said decision indicative of the degree of similarity to the person to be examined by an acoustic output and/or photoelectric display.