A method for manufacturing packaging material and sheets, such as disposable food containers or seedling-breeding containers from straws, comprising pulverizing into powder, with 20-50 mesh; stirring the powder of straw, a binder, a lubricant and water in weight parts of 70-88, 0.3-1.0, 0.05-1 and 10-20 respectively, at ambient temperature for 5-15 minutes under 50-80 rpm to obtain a mixture, and thermal molding the mixture at a temperature of 100-150.degree. C., and under a pressure of 20-250 MPa.