To conveniently carry and keep an assembling child chair at the time of going-out and to easily abondon it by forming a fold and a notch, etc., in ona planar chair main body and fitting a planar reinforcing leg part and a fixing tool for fixing a seat surface part and a back surface part where the notch or the notch and the fold are independently formed in order to reinforce the seat surface part and the back surface part.

One planar chair mainbody 1 is bent so as to form the seat surface part 4, the back surface part 5, a right side surface leg part 6 and a left side surface leg part 7. Then, the inserting projection B16 of a right front surface leg part 18 which is bent under the seat surface part 4 is inserted and fixed to the insertion hole B13 of a left front surface leg part 19 which is bent in the same way. The inserting projection A15 of the seat surface part 4 is inserted to the insertion hole A12 of the back surface part 5 and the fixing tool is inserted to a fixing tool insertion hole 22 in the inserting projection A15 so as to execute fixing. Then, the notch A9 of the reinforcing leg part is combined with the notch A9 of the back surface part 5 and the notch B is combined with the seat surface lower leg part 20 which is bent under the seat surface part 4 so as to reinforce the seat surface part 4 and the back surface part 5.