Numerical modeling of convection of powder was performed. Convection of powder occurs when a strong vertical vibration is applied. When the control parameter, the acceleration amplitude r, exceeds some critical value Γc, convection and heaping start. In our simulation, the powder is modeled with a discrete elementary method but without rotation and with isotropic linear visco-elastic interaction. The convection is reproduced and Γc turns out to be about the gravity acceleration g, which agrees with experimental findings. Another remarkable phenomena, surface fluidization, is also reproduced and the critical value Γc'again agrees with experimental findings. It is suggested that this convection is caused by the instability of powder induced by the elastic interaction.