An electrical connection device comprises a first connector and a second connector which are mated with each other. The first connector comprises a first insulative housing and a first terminal group. Two terminals of the first terminal group are first protruding terminals, and one other terminal of the first terminal group is a first non-protruding terminal. The second connector comprises a second insulative housing and a second terminal group. At least one terminal of the second terminal group is second protruding terminal and two other terminals of the second terminal group are second non-protruding terminals so that the number of the second protruding terminal is less than the number of the first protruding terminals. The second protruding terminal mates with one of the first protruding terminals and one of the first protruding terminals mates with a second non-protruding terminal.