A heat cap is provided for applying heat to hair on a user's head, primarily to a pile or row of hair along the top of the user's head. The heat cap is shaped to conform substantially to the shape of the user's head with the pile of hair thereon so as to apply heat evenly to the hair. The heating coil is disposed in the heat cap only in those areas where heat is desired for the hair and is absent in areas of the heat cap where it is undesirable to apply heat to the head. An adjustable flap on each side of the heat cap enables the size of the cap to be adjusted to fit different users. The adjustable flaps also tend to hold the cap outward away from the ear and lower sides of the head and can be easily opened to enable access to the user's ear while the heat cap is being worn. An electrical thermostat automatically brings the heat cap to an optimal temperature and maintains the temperature during the desired conditioning period. The heat cap is manufactured by cutting a plurality of similarily shaped flat pieces and joining them together along certain corresponding sides.