Provided is a building material manufacturing apparatus and a building material manufacturing method that are suitable for efficiently manufacturing a building material while suppressing clogging of a sieve portion for sieving the building raw material. The building material manufacturing apparatus of the present invention includes, for example, a sieve portion 10 and a receiving tool 30. The sieve portion 10 includes a receiving and sending sheet 11 with no sieve openings, onto which the building raw material M is dropped, and at least one sieve sheet 12 with sieve openings that is located below the sheet. The receiving and sending sheet 11 and the sieve sheet 12 can perform undulating motion, are inclined, and are arranged side by side in the inclination direction. The receiving tool 30 is for receiving the building raw material M that has passed through the sieve openings of the sieve portion 10. In the building material manufacturing method of the present invention, for example, in a state in which the receiving and sending sheet 11 and the at least one sieve sheet 12 are performing undulating motion, the building raw material M is dropped onto the receiving and sending sheet 11, moved from the receiving and sending sheet 11 onto the sieve sheet 12, subjected to sieving by the sieve sheet 12, and the portion that passes through the sieve openings of the sieve sheet 12 is accumulated on the receiving tool 30, whereby a mat with at least one layer is formed.