To provide an orthogonal section form capable of forming various footing widths at an orthogonal section between a foundation having a footing and the other foundation.

This orthogonal section form 10 is used for forming the orthogonal section between the foundation A having the footing F and the other foundation B with a different section. The orthogonal section form 10 comprises a metal main form 30 and a metal slide frame 50 slidably engaged with the main form 30. The footing width is adjustable by sliding the slide frame 50.