PROBLEM TO BE SOLVED: To provide an oscillation element using a plurality of negative resistance elements in which all negative resistance elements arranged in an antenna oscillate electromagnetic waves having arranged frequency and phase synchronously, thus enhancing the oscillation output.SOLUTION: The oscillation element includes a single or a plurality of antennas for guiding electromagnetic waves, and a plurality of negative resistance elements 101 connected electrically in series with the antenna and connected in parallel with each other. The plurality of negative resistance elements 101 are disposed only at a position where the electromagnetic waves oscillated by respective negative resistance elements 101 have the substantially same phase, or a position where the electromagnetic waves have the substantially reverse phase. The position where the electromagnetic waves have the substantially same phase or reverse phase can be regarded as the position where the oscillation frequencies of respective negative resistance elements 101 are equal.