Abstract: A machining device equipped with a spindle position interchanger comprises a longitudinal table provided on a bed and movable in a horizontal direction; a transverse table provided on the longitudinal table and movable in a direction perpendicular to the longitudinal table; a column erected on the transverse table and turnable in a horizontal plane; a first spindle head vertically movable along the column; a second spindle head provided at a position different from (at a position at 1800° to, or opposite to) the position of the first spindle head and vertically movable along the column independently of the first spindle head; a first main spindle and a second main spindle attached to the first spindle head and the second spindle head, respectively; a tool change arm for changing a tool in the second main spindle; and a tool magazine mounted on an upper portion of the column for housing many tools.