A connecting device includes a connecting member, a slider, and a blocking assembly. The connecting member includes a first sliding slot and a limiting slot formed at one end of the connecting member. The slider includes a second sliding slot and an accommodating hole formed at one end of the slider. The second sliding slot is configured to slidably engage with the first sliding slot. The slider further includes a through hole formed on a side wall of the slider and configured to communicate with the accommodating hole. The blocking assembly includes a limiting button and a limiting column. The limiting button includes a transmission portion configured to be received in the through hole. The limiting column is configured to be accommodated in the limiting slot and the accommodating hole. The limiting column includes a receiving hole configured to receive the transmission portion.