There is provided an insulation material having a dielectric constant of 10 or more, comprising a filler having a dielectric constant of 50 or more and having two peaks in different particle size ranges in a particle size distribution and an insulating resin combined with each other; an insulation material having a dielectric constant of 10 or more comprising, as essential components, 1) at least one filler selected from the group consisting of barium titanate, strontium titanate, potassium titanate, magnesium titanate, lead titanate, titanium dioxide, barium zirconate, calcium zirconate and lead zirconate, 2) an insulating resin and 3) a dispersant containing a carboxylic group; or an insulation material comprising a filler having a dielectric constant of 50 or more, a dispersant for dispersing the filler and an insulating resin as essential components, wherein an extract of a cured product of the insulation material obtained by extraction with water at 120.degree. C. for 20 hours using a pressure vessel has a pH of 6 or higher.