A mixing and blending method for powdered or granular material includes supplying pulsating vibration air into an airtight tank from a bottom thereof. An airtight tank having a porous bottom plate on which the material is stored is provided for the mixing and blending method. In the system pulsating vibration air is generated by periodically increasing and decreasing the amount of blowing air at a low frequency. Pulsating vibration air is introduced into the airtight tank from the bottom of the airtight tank so as to generate air flow going upward through the porous bottom of the airtight tank. As a result, powdered or granular material stored on the porous bottom plate in the airtight tank is uniformly mixed and blended in the airtight tank while continuously moving up and down as in a convectional manner.