A probe shape detection apparatus includes a magnetic field sensing section for sensing a magnetic field generated by an electromagnetic coil in a flexible probe, a movement speed calculation section for calculating a movement speed of the coil, a coordinate computation section for calculating three-dimensional coordinates of the coil based on the sensed magnetic field, a moving average coordinate calculation section for calculating moving average coordinates of the coil, a comparison section for comparing the calculated movement speed with a predetermined threshold, a coil coordinate setting section for setting one of the moving average coordinates and the three-dimensional coordinates calculated by the coordinate computation section as the three-dimensional coordinates of the coil, based on a comparison result of the calculated moving speed, and a signal processing section for generating a video signal to display a shape of the probe, based on the set three-dimensional coordinates of the coil.