In a blower fan according to a preferred embodiment of the present invention, a side wall portion includes a tongue portion arranged to project between an air outlet and an impeller. A side surface of the tongue portion includes a tongue portion tip arranged to touch a first imaginary plane including a central axis; a first tongue portion side surface arranged to extend from the tongue portion tip along an outer envelope of the impeller; and a second tongue portion side surface arranged to extend from the tongue portion tip toward a side edge, the side edge being a line of intersection of the air outlet and the side wall portion. The second tongue portion side surface is arranged to cross a second imaginary plane including the central axis and touching the side edge.