To provide a square secondary battery with a high reliability.
A square secondary battery (20) including an electrode body (3) having a positive electrode plate and a negative electrode plate, a square outer package (1) that includes an opening and that houses the electrode body (3), and a sealing plate (2) that seals the opening of the square outer package (1), in which an inner side insulating member (12) serving as a first insulating member is disposed between the sealing plate (2) and a negative electrode collector member (8) and is fixed to the sealing plate (2), and in which a second insulating member (80) disposed between the sealing plate (2) and the electrode body (3) is connected to the inner side insulating member (12) serving as the first insulating member.