A magnetic sensor for detecting the intensity of a magnetic field in three axial directions, in which a plurality of giant magnetoresistive elements are formed on a single semiconductor substrate. A thick film is formed on the semiconductor substrate; giant magnetoresistive elements forming X-axis and Y-axis sensors are formed on a planar surface thereof; and giant magnetoresistive elements forming a Z-axis sensor are formed using slopes of channels in the thick film. Each of the slopes of the channels can be constituted of a first slope and a second slope, so that a magneto-sensitive element is formed on the second slope having a larger inclination angle. In order to optimize the slope shape and inclination with respect to each channel, it is possible to form a dummy slope that does not directly relate to the formation of the giant magnetoresistive elements.