Provided is a seat heater that is a seat (901) including: a planer heating element (101) that has a plurality of electric heating wires on its upper surface and that includes a fiber layer (101b); a cushion member (902) that locates over a lower surface of the planer heating element (101); and a skin (903) that locates above the planer heating element (101), wherein the planer heating element (101) has, in voids of the fiber layer (101b), a silica aerogel that is a silica porous body having pores with a mean pore diameter of 10 nm to 68 nm.
