The invention provides a motion detection apparatus that can improve a noise removal effect, can suppress the occurrence of tailing of a motion portion resulting from the increase of the noise removal effect, can increase the noise removal effect from a high electric field to a low electric field and can eliminate unnaturalness of the image for observation such as an after-image and a pasting feel resulting from the increase of the noise removal effect, and a noise reduction apparatus using the motion detection apparatus. The motion detection apparatus compares a frame difference with a threshold value, calculates the sum of the comparison result for a block including a plurality of pixels, and applies in expansion the output to several pixels in a horizontal or vertical direction to detect motion. The noise reduction apparatus utilizes this motion detection apparatus.