lock mechanism 130 c for maintaining the spread state of the frame body has a lock pin 190 c having a recessed portion at its leading end and a cylindrical member 192 c fixed to the frame piece 112 c and having two grooves 194 c 196 c formed diagonal positions as shown in fig1 a to 12c a spring is connected to the lock pin 190 c so that the lock pin 190 c may fit in one of the two grooves 194 c 196 c by the elastic force of the spring the other lock mechanisms 132 c 134 c 130 d to 134 d have the same configuration as that of the lock mechanism 130 c in the portable screen 2 according to embodiment 2 as shown in fig1 a to 13c from the locked state in which the frame pieces 112 c and 114 c are folded and the lock pin 190 c fits into the groove 196 c the hinge member 140 c is rotated in a direction of arrow a and thereby the fitting state of the lock pin 190 c and the groove 196 c is released and the locking of the lock mechanism 130 c is released further in this state by further rotating the hinge member 140 c in a direction of arrow b the lock pin 190 c slidingly moves on the side surface of the cylindrical member 192 c then when the frame body 110 is in the spread out state the lock.