There is provided a small-sized portable microwave plasma generator capable of generating plasma at atmospheric pressure with low electric power including a coaxial cable, an outer conductor, a connection conductor, and a connection member. The coaxial cable includes a first inner conductor and a dielectric material encircling the first inner conductor. The outer conductor encircles the coaxial cable. The connection conductor includes at least one gas inlet tube. The connection conductor electrically connects between the first inner conductor and the outer conductor at one end of the coaxial cable. The connection member includes a second inner conductor passing through the outer conductor and then connecting to the first inner conductor.