A collapsible toilet made from a rectangular board demarcated into five rows × three columns (L,C,R) of rectangular segments (1L-5R) by foldable division lines or perforation lines, the segments being formed to be bilaterally symmetric with respect to a line perpendicular to a row direction as a symmetry axis, the rectangular board being shaped into a rectangular parallelepiped when assembled, the toilet comprising: a first row section that forms a first side face; a second row section that is adjacent to the first row section and forms a top face; a third row section that is adjacent to the second row section and forms a third side face opposite to the first side face; a fourth row section that is adjacent to the third row section and forms at least a second side face, a fourth side face opposite to the second side face, and a bottom face; and a fifth row section that is adjacent to the fourth row section and forms a first reinforcing portion for the top face, a second reinforcing portion for the top face, and the first side face, wherein an opening (2Ca, 2Ra, 2La) is formed in the top face, during the assembly, the first reinforcing portion and the second reinforcing portion are each formed into a wave-shape portion by a plurality of division lines orthogonal to the row direction, and the first reinforcing portion and the second reinforcing portion can be placed along the second side face and the fourth side face, respectively, over the entire areas of the respective side faces, the second row section is formed of a center second segment and a right second segment and a left second segment placed with the center second segment interposed therebetween, the collapsible toilet being characterised in that at least one of the right second segment and the left second segment, and the center second segment are folded along a predetermined segment line and laid on top of each other, thereby forming the top face, and the one of the right second segment and the left second segment, and the center second segment have respective openings (2Ca, 2Ra, 2La), and the openings (2Ca, 2Ra, 2La) are in communication with each other. a first row section that forms a first side face; a second row section that is adjacent to the first row section and forms a top face; a third row section that is adjacent to the second row section and forms a third side face opposite to the first side face; a fourth row section that is adjacent to the third row section and forms at least a second side face, a fourth side face opposite to the second side face, and a bottom face; and a fifth row section that is adjacent to the fourth row section and forms a first reinforcing portion for the top face, a second reinforcing portion for the top face, and the first side face, wherein an opening (2Ca, 2Ra, 2La) is formed in the top face, during the assembly, the first reinforcing portion and the second reinforcing portion are each formed into a wave-shape portion by a plurality of division lines orthogonal to the row direction, and the first reinforcing portion and the second reinforcing portion can be placed along the second side face and the fourth side face, respectively, over the entire areas of the respective side faces, the second row section is formed of a center second segment and a right second segment and a left second segment placed with the center second segment interposed therebetween, the collapsible toilet being characterised in that at least one of the right second segment and the left second segment, and the center second segment are folded along a predetermined segment line and laid on top of each other, thereby forming the top face, and the one of the right second segment and the left second segment, and the center second segment have respective openings (2Ca, 2Ra, 2La), and the openings (2Ca, 2Ra, 2La) are in communication with each other.