A coaxial connector device includes a first signal contact member joined to a central conductor of a first coaxial cable, a second signal contact member joined to a central conductor of a second coaxial cable, a ground contact member has an annular fitting portion arranged around the first and second signal contact members and is joined to the outer conductors of the respective first and second coaxial cables, and a flat partition provided with a ground potential and located between the first signal contact member and the second signal contact member.