PURPOSE: To provide an anti-icing air valve for a pneumatic motor which can provide a low friction for a slide member.

CONSTITUTION: An air valve 10 is composed of a housing 12 defining therein a valve chamber 60 communicated with a compressed air source, a slide 14 slidably arranged in the valve chamber 10 so as to carry out reciprocating motion, a first and a second port plate 36 respectively having a first and a second exhaust port 42, and a first and a second piston chamber port 40, and a first and a second valve cup 16 located in the slide 14. The valve cup 16 incorporating sealing surfaces 18a which are arranged therearound, guides compressed air fed from the valve chamber 10, into piston chambers, alternately, and the guides it into the exhaust ports 42 when the slide 14 reciprocates.