Pneumatic radial tire with tread having blocks having waved sipes

The present invention provides a pneumatic radial tire which is, by effectively suppressing collapse-deformation of a relatively large magnitude in sectioned portions of each block, which sections are demarcated by sipes, and also effectively preventing the sipe from making narrowing-deformation, excellent in not only driving performance and braking performance on an icy or snowy road but also driving stability on a general road. The tire characteristically includes: a tread having a contact surface 1; plural circumferential grooves 2; plural lateral grooves 3; blocks 4 demarcated by the circumferential grooves and the lateral grooves in the contact surface of the tread; and plural sipes 5 provided in the blocks 4, wherein the bottom portion of each sipe 5 is provided with at least one upward-protruding projection 7 for integrally connecting respective facing groove walls of the sipe 5.