A position determination system (100; 400) comprising: a personal portable terminal that is to be carried by a person whose position is determined; and a position determination apparatus that determines the position of the personal portable terminal, wherein the personal portable terminal includes a personal terminal side transmitter that transmits a position determination signal to be used for position determination to the position determination apparatus, and a personal terminal side controller that controls the personal terminal side transmitter, wherein the position determination apparatus includes a plurality of first and second position determination side receivers (22A, 22B, 23A, 23B) that are arranged at different first and second positions which are spaced at first and second distances away from the personal portable terminal, respectively, to receive the position determination signal which is transmitted by the personal terminal side transmitter, the second distance being greater than the first distance, and a position determination side calculator that determines the position of the personal portable terminal based on a difference between an intensity of the position determination signal that is received by the first position determination side receivers (22A, 22B) and an intensity of the position determination signal that is received by the second position determination side receivers (23A, 23B), wherein the position determination side calculator evaluates a conditional expression in which whether a difference between an average of radio wave intensities of the position determination signal that are received by the first position determination side receivers (22A, 22B) and an average of radio wave intensities of the position determination signal that are received by the second position determination side receivers (23A, 23B) is greater than a predetermined threshold is decided to determine the position of the personal portable terminal. a personal portable terminal that is to be carried by a person whose position is determined; and a position determination apparatus that determines the position of the personal portable terminal, wherein the personal portable terminal includes a personal terminal side transmitter that transmits a position determination signal to be used for position determination to the position determination apparatus, and a personal terminal side controller that controls the personal terminal side transmitter, wherein the position determination apparatus includes a plurality of first and second position determination side receivers (22A, 22B, 23A, 23B) that are arranged at different first and second positions which are spaced at first and second distances away from the personal portable terminal, respectively, to receive the position determination signal which is transmitted by the personal terminal side transmitter, the second distance being greater than the first distance, and a position determination side calculator that determines the position of the personal portable terminal based on a difference between an intensity of the position determination signal that is received by the first position determination side receivers (22A, 22B) and an intensity of the position determination signal that is received by the second position determination side receivers (23A, 23B), wherein the position determination side calculator evaluates a conditional expression in which whether a difference between an average of radio wave intensities of the position determination signal that are received by the first position determination side receivers (22A, 22B) and an average of radio wave intensities of the position determination signal that are received by the second position determination side receivers (23A, 23B) is greater than a predetermined threshold is decided to determine the position of the personal portable terminal.