A compound semiconductor device disclosed herein includes: a GaN carrier transit layer formed on a substrate; a barrier layer formed on the carrier transit layer; a first recess and a second recess formed in the barrier layer; a first InAlN layer and a second InAlN layer formed in the first recess and the second recess respectively, a composition ratio of In in the InAlN layers being equal to or more than 17% and equal to or less than 18%; a source electrode formed on the first InAlN layer; a drain electrode formed on the second InAlN layer; and a gate electrode formed on the barrier layer.