A method for manufacturing a solid product containing nitrogen and phosphor, particularly a solid ammonium phosphate and/or urea ammonium phosphate product, in which method the solution containing urea and phosphoric acid is heated. Water then evaporates from the solution and the urea in the solution decomposes into ammonia and carbon dioxide. The carbon dioxide exits the reactor together with water vapour; the generated ammonia neutralizes the phosphoric acid. A suspension containing ammonium phosphate and/or urea ammonium phosphate is obtained, which is solidified, dried, crushed, ground and/or granulated. The end product as such can be used as a fertilizer or it can be used as part of a mixed fertilizer.