A light-emitting device (12) includes a base (14) and two red light-emitting chips (22), two green light-emitting chips (24) and a blue light-emitting chip (26) arranged on the base red, green, blue, green, red in a left-to-right order. The red light-emitting chips, the green light-emitting chips and the blue light-emitting chip include a plurality of red-color quantum dots, green-color quantum dots and blue-color quantum dots respectively. A planar light source (10) includes a planar plate (102), and a plurality of the light-emitting devices arranged in an array on the planar plate. A direct type backlight module (20) includes a diffusing sheet (18) and the planar light source facing a surface of the diffusing sheet.