A chemical toilet cabin comprising: - a platform, vertical side walls (4, 5, 6, 7), and a roof, - reversible joint connection means (9, 10, 11, 12, 21, 22) formed along the edges of said side walls and on opposed faces of said platform and said roof to amovably join each side wall to the side walls adjacent thereof, to the platform and to the roof, - reversible locking means (13, 14, 15) of said joint connection arranged between a side wall and the adjacent wall and between each of said side walls and said platform and said roof, characterized in that - said side walls (4, 5, 6, 7) have vertical edges (4a,b; 5a,b; 6a,b; 7a,b) and side wall portions (4c, 5c, 6c, 7c) adjacent to said vertical edges that are rounded in such a way to form a rounded edge of the cabin when two side walls are paired to each other; - the vertical edges (4a,b; 5a,b; 6a,b; 7a,b) delimiting said rounded portions (4c, 5c, 6c, 7c) of said vertical walls are shaped with matching profiles (21, 22) of the male-female type between a wall and the adjacent wall making up said joint connection means between adjacent walls; - each of said reversible locking means of said joint connection means provided between two adjacent side walls comprises a lever lock comprising an articulated system formed by a first arm with a hook-shaped end and a second arm lying in a plane perpendicular to said two adjacent side walls and pivotally connected to said first arm and to a rounded portion of one of said adjacent side walls about axes perpendicular to said plane; - the hook-shaped end of said first arm being engaged with a tooth formed on a rounded portion of the other of said two adjacent side walls in a tightened condition when said second arm is rotated beyond a dead centre of said articulated system. - a platform, vertical side walls (4, 5, 6, 7), and a roof, - reversible joint connection means (9, 10, 11, 12, 21, 22) formed along the edges of said side walls and on opposed faces of said platform and said roof to amovably join each side wall to the side walls adjacent thereof, to the platform and to the roof, - reversible locking means (13, 14, 15) of said joint connection arranged between a side wall and the adjacent wall and between each of said side walls and said platform and said roof, - said side walls (4, 5, 6, 7) have vertical edges (4a,b; 5a,b; 6a,b; 7a,b) and side wall portions (4c, 5c, 6c, 7c) adjacent to said vertical edges that are rounded in such a way to form a rounded edge of the cabin when two side walls are paired to each other; - the vertical edges (4a,b; 5a,b; 6a,b; 7a,b) delimiting said rounded portions (4c, 5c, 6c, 7c) of said vertical walls are shaped with matching profiles (21, 22) of the male-female type between a wall and the adjacent wall making up said joint connection means between adjacent walls; - each of said reversible locking means of said joint connection means provided between two adjacent side walls comprises a lever lock comprising an articulated system formed by a first arm with a hook-shaped end and a second arm lying in a plane perpendicular to said two adjacent side walls and pivotally connected to said first arm and to a rounded portion of one of said adjacent side walls about axes perpendicular to said plane; - the hook-shaped end of said first arm being engaged with a tooth formed on a rounded portion of the other of said two adjacent side walls in a tightened condition when said second arm is rotated beyond a dead centre of said articulated system.