An apparatus for opening and closing a sliding armrest console, in which it is easy to access a console storage space by inserting an armrest into an armrest console in a state in which the console is opened, may include an armrest rotating about a main hinge, a console, an upper portion of which is closed by the armrest, a first guide groove formed for guiding a movement direction of an auxiliary hinge positioned at the armrest when the armrest rotates, and a main guide groove formed in a vertical direction of the console such that the main hinge moves along the main guide groove, wherein when the main hinge moves along the main guide groove, the auxiliary hinge moves along a second guide groove, which is vertically connected to the first guide groove, so that the armrest is inserted into the console.