A polysiloxane composition

A composition, which contains:

• a component (A), that is an organopolysiloxane, preferably a component (A-1) that is an organopolysiloxane having two or more alkenyl groups per molecule;
• optional a component (B) that is an organohydrogenpolysiloxane having two or more hydrogen atoms directly bonded to silicon atoms and is contained in such an amount that the number of moles of hydrogen atoms directly bonded to silicon atoms in the component (B) is 0.1 to 5.0 times the number of moles of alkenyl groups derived from the component (A-1);
• a component (C) that is a heat conductive filler
• (C) component contains
• 10-25 wt % (C-1) aluminum hydroxide with an average particle diameter greater than or equal to 0.1 μm and less than or equal to 4 μm,
• 18-37 wt % (C-2) aluminum hydroxide with an average particle diameter of 4 μm or more and 20 μm or less,
• 48-65 wt % (C-3) aluminum hydroxide with an average particle diameter greater than or equal to 80 μm and less than or equal to 100 μm,
• in (C-1), (C-2) and (C-3), the component (C) in the composition is calculated as 100 wt %,
• optional a component (D) that is a platinum group metal-based curing catalyst having a platinum group metal element content of 0.1 to 1,000 ppm relative to the component (A-1) based on mass, wherein the filling rate of the heat conductive filler is greater than or equal to 0.88.