A relative rotational position detection apparatus for detecting a relative rotational position between first and second shaft sections (1, 2) rotatable relative to each other, said relative rotational position detection apparatus comprising: a first sensor for detecting a rotational position of the first shaft section in a noncontact fashion and generating a first output signal by phase-shifting a reference A.C. signal in accordance with the detected rotational position of said first shaft section; a second sensor for detecting a rotational position of the second shaft section in a noncontact fashion and generating a second output signal by phase-shifting the reference A.C. signal in accordance with the detected rotational position of said second shaft section; and an output circuit for outputting a first timing signal, consisting of a zero cross detection pulse of said first output signal and corresponding to a phase shift amount of said first output signal and for outputting a second timing signal, consisting of a zero cross detection pulse of said second output signal and corresponding to a phase shift amount of said second output signal, via respective output lines (7a, 7b), wherein relative rotational position detection data is outputted via the two output lines extending from said output circuit, and the relative rotational position detection data appears in a time difference between said first timing signal and said second timing signal, characterized in that said first sensor, second sensor and output circuit are accommodated together in a single case, said respective output lines (7a, 7b) being derived from the single case, and that said relative rotational position detection apparatus further comprises: a computer having two input terminals to be connected with said respective output lines (7a, 7b) derived from the single case in order to input said first and second timing signals (Lp1, Lp2) via said respective output lines (7a, 7b), said computer performing a process for acquiring measurement data of the relative rotational position by measuring a time difference between the first timing signal and second timing signal inputted to the input terminals. a first sensor for detecting a rotational position of the first shaft section in a noncontact fashion and generating a first output signal by phase-shifting a reference A.C. signal in accordance with the detected rotational position of said first shaft section; a second sensor for detecting a rotational position of the second shaft section in a noncontact fashion and generating a second output signal by phase-shifting the reference A.C. signal in accordance with the detected rotational position of said second shaft section; and an output circuit for outputting a first timing signal, consisting of a zero cross detection pulse of said first output signal and corresponding to a phase shift amount of said first output signal and for outputting a second timing signal, consisting of a zero cross detection pulse of said second output signal and corresponding to a phase shift amount of said second output signal, via respective output lines (7a, 7b), wherein relative rotational position detection data is outputted via the two output lines extending from said output circuit, and the relative rotational position detection data appears in a time difference between said first timing signal and said second timing signal, characterized in that said first sensor, second sensor and output circuit are accommodated together in a single case, said respective output lines (7a, 7b) being derived from the single case, and that said relative rotational position detection apparatus further comprises: a computer having two input terminals to be connected with said respective output lines (7a, 7b) derived from the single case in order to input said first and second timing signals (Lp1, Lp2) via said respective output lines (7a, 7b), said computer performing a process for acquiring measurement data of the relative rotational position by measuring a time difference between the first timing signal and second timing signal inputted to the input terminals.