An apparatus for detecting an angular position of a crankshaft of an internal combustion engine includes a disk which is rotatable in synchronism with the rotation of the crankshaft, a row of magnetic elements disposed on the disk along a circumferential periphery thereof at circumferentially equal intervals, an electromagnetic pick-up device disposed orthogonally to a plane of rotation of the disk in opposition to the row of magnetic elements, and a shaping circuit for shaping an output signal of the electromagnetic pick-up device into a rectangular waveform signal. The shaping circuit is combined integrally with the electromagnetic pick-up device into a single unit to prevent external noise from being superposed on the output signal from the pick-up device. The shaping circuit includes an integrator for integrating the output signal to produce a reference signal for the comparator. Additionally, the shaping circuit may include a rectifying/smoothing circuit for rectifying and smoothing the output signal of the pick-up device to produce a level signal, and a high-pass filter circuit having a cut-off frequency which is variable in dependence on a change in the level signal. The output signal of the pick-up device is input to the comparator after having passed through the high-pass filter circuitry so that a pulsating noise component superposed on the pick-up output signal and having a frequency corresponding to the engine rotation speed is satisfactorily eliminated. Thus, accuracy and reliability of the engine control can be remarkably improved.