A magnetic sensor includes a waveguide, a first electrode, a second electrode, and a detection electrode. In the waveguide, a first position, a detection position, and a second position are arranged in this order. The first electrode excites a first spin wave. The first spin wave is propagated from the first position to the detection position. The second electrode excites a second spin wave. The second spin wave is propagated from the second position to the detection position. The detection electrode extracts a signal from the detection position.