Abstract: A keyboard apparatus includes a key matrix having key switches disposed at intersections between rows and columns forming a matrix and a control unit for selecting a row and a column of the key matrix to sense a state of a key switch disposed at an intersection of the selected row and the selected column of the key matrix. The apparatus includes a first confirmation unit for sensing, in a first period of time, a key switch state of the key matrix to confirm whether or not two or more depressed keys exist on a row of the key matrix and a second confirmation unit for sensing again, in a second period of time, a key switch state of the key matrix such that when two or more depressed keys exist on a column of the key matrix, a confirmation is made to determine whether or not two or more depressed keys exist on the row on which the key depression is found in the key matrix.