The purpose of this study was to examine the physiological characteristics of top-level youth soccer players and their positional characteristics during an official game as a case study, and to obtain basic materials for future research. Three youth soccer players （FW, MF, and DF） of Sanfrecce Hiroshima F.C. youth team were analyzed by measuring their heart rate （HR） during one official game in which they were in the starting lineup. As a result, the following four points became clear:（ 1） the HR during the game periodically fluctuated up and down between 130-200bpm, （2） average HR were 180.7±10.9 bpm for FW player, 175.8±9.5 bpm for MF player, and 169.6±11.6 bpm for DF player, （3） regarding to the HR distribution, although the "High" category was the highest for all players in the whole game, in the second half, there was a significant decrease in the "Maximum" category for FW player, and the highest category for DF player changed from "High" to "Moderate," and （4） HR during the game was, in descending order, FW > MF > DF.