Abstract: A flexible pivotal device for a mannequin joint is arranged in a lower limb of a mannequin and comprises a female connection member and a male connection member. The female connection member includes a first fixing plate, a first fixing disc and a first engagement member. The first fixing plate has two installation holes. The male connection member is coupled to the female connection member and includes a second fixing disc; a connection element having two sleeves respectively inserted through two installation holes and moveable thereinside, and a second engagement member engaged with the first engagement member; and a second fixing plate arranged between the second fixing disc and the connection element, locked to the second fixing disc, and having two hooks respectively coupled to two elastic elements arranged inside the sleeves. The sleeves can be pulled away from the second fixing plate to a certain degree.