Fig. 1 shows the appearance of the boards made from whole particles and whole powder. The boards made from whole particles could be easily divided into particles by hand, resulting in falling apart before testing. In contrast, the boards were successfully manufactured from whole powder. Fig. 2 shows the morphological effect on IB. The IB of whole powder was 0.05 MPa, lower than 0.15 MPa which is the minimum requirement for Type-8 of particleboard (JIS A5908, 2003). However, it was confirmed that rice straw binderless boards can be manufactured by a simple method based on grinding and hot-pressing process.