A keyboard device includes plural keys, a supporting plate and a membrane switch circuit member. The membrane switch circuit member includes a first board, a second board, a third board and a fourth board. The first board includes plural first contacts. The second board includes plural second contacts and plural first openings. The third board includes plural third contacts and plural second openings. The fourth board includes plural fourth contacts. The plural first contacts, the plural first openings and the plural third contacts are collaboratively defined as a first key matrix. The plural second contacts, the plural second openings and the plural fourth contacts are collaboratively defined as a second key matrix.