A back plate, a method for manufacturing the back plate and a backlight module are provided. The method for manufacturing the back plate includes the following steps. A main body is provided. The main body includes a bottom portion and at least one sidewall connected to the bottom portion. The sidewall has a plurality of grooves, and each of the grooves has a first side surface and a second side surface. A first recess and a second recess corresponding to the first recess are respectively disposed on the first side surface and the second side surface. An external force is applied on the bottom portion to form each of the bottom portion and the sidewalls into arc shape, in which the first side surface contacts the second side surface of each groove, and a hole portion is formed between the first recess and the second recess.