To efficiently produce a board for building having a laminate of a base layer, a kneaded material and a protective sheet.

The apparatus for manufacturing a board for building comprises an upper main roller 4 and a lower main roller 6 vertically arranged via a conveying route P of a base layer 2 at a gap, conveying means 9, 10, 12 and 18 for conveying the layer 2 toward the gap of the rollers 4, 6, an unwinding roller 30 on which a protective sheet 32 is wound, a sub-roller 20 arranged at a gap to the roller 4, and a kneaded material supply means 22 for supplying a kneaded material 24 to an upper side of the gap of the rollers 4 and 20.