A heater includes a substrate, a plurality of first electrode down-leads, a plurality of second electrode down-leads and a plurality of heating units. The plurality of first electrode down-leads are located on the substrate in parallel to each other and the plurality of second electrode down-leads are located on the substrate in parallel to each other. The first electrode down-leads cross the second electrode down-leads and define a plurality of grids. One heating unit is located in each grid. Each heating unit includes a first electrode, a second electrode and a heating element. The heating element includes a carbon nanotube structure.