To provide a superior heat insulation material for exhibiting high heat insulation performance even in an incomplete moistureproof environment, and manufacturable by a relatively simple method.

This heat insulation material uses silica having physical properties of (a) the pore volume of 1.6 ml/g or more, (b) the moisture content of 15 wt% or less, and (c) the whole carbon concentration of 0.1 wt% to 15 wt%.