A method of assembling an electronic device according to the present disclosure is described below. The positioning posts 221A of the waterproof component 220 pass through the through holes 211B on the supportive sheet metal 211 of the base 210, respectively, to position the waterproof component 220 on one side of the supportive sheet metal 211. Then, the movable latch lid 230 covers the other side of the supportive sheet metal 211 to allow the positioning posts 221A to abuttingly fit to the passages 231 on the movable latch lid 230, respectively. Next, the rod portions 241A of the coupling elements 240 pass from the outer side of the movable latch lid 230 through the passages 231 and then through the through holes 211B of the supportive sheet metal 211 before being fastened and fixed to the positioning posts 221A of the waterproof component 220, respectively, so as for the head portions 241B to stop at the outer side of the movable latch lid 230, for the movable latch lid 230 to be fixed to the waterproof component 220, and for the movable latch lid 230 to slide relative to the rod portions 241A through the passages 231. After that, the securing sheet metals 212 of the base 210 are fixed to one side of the opening 110 to allow the supportive sheet metal 211 to rotate relative to the securing sheet metals 212, and the waterproof lid structure 200 is shut to allow the seal portion 222 of the waterproof component 220 to cover and hermetically seal the opening 110. Finally, users push the handle 232 to drive the movable latch lid 230 to move along the direction of extension of the passages 231 to thereby reach a fastening position and cause the resilient hook 234 to engagingly fit to the right side of the dowel 221B, allowing the latch portions 233 to be latched into the fastening grooves 111 to thereby fasten the movable latch lid 230 in place.