A thermally assisted magnetic head slider includes an air bearing surface facing to a magnetic recording medium, a read portion, and a write portion including a write element, a waveguide for guiding light generated by the light source module, and a plasmon unit provided around the write portion and the waveguide. A first coat layer with a first thickness which has a first light absorption index is covered on an opposed-to-medium surface of the read portion, and a second coat layer with a second thickness which has a second light absorption index is covered on an opposed-to medium surface of the write portion, wherein the second thickness is larger than the first thickness, and the second light absorption index is smaller than the first light absorption index. The slider can protect the write portion and improve the reading performance of the read portion.