The invention concerns a bath lift device (10) for raising and lowering persons into or out of a bathtub comprising: - a chassis (11) to rest on a portion of the bath tub； - a seat plate (21) and a backrest (22) pivotally connected thereto, said backrest being pivotally movable relative to said seat plate between three rest positions, i.e. an upright rest position, corresponding to the normal position of use, a rear rest position, in which the backrest is positioned rearward relative to the upright rest position, and a front rest position, in which the backrest is positioned forward relative to the upright position； - a lifting means for adjusting the height of the seat plate (21) between a lowermost end position and an uppermost end position, the lifting means comprising a driving means (23) mounted to the backrest (22) and a lifting member (24) to be actuated by the driving means (23)； - a bearing support (25) secured to the chassis (11) and provided with a cam profile (253) in which a lower end of the lifting member (24) is engaged so as to permit the movement of the backrest (22) between the rear rest position and the upright rest position； - at least one locking lever (31), that is pivotally connected to the backrest (22), said locking lever being adapted to define at least one first locking position, in which the locking lever (31) prevents a pivoting movement of the backrest (22) relative to the seat plate (21) in the upright rest position of the backrest (22) when the lifting member (24) extends over a specific extension length and permits said pivoting movement when the lifting member (24) is retracted under said specific extension length.
