The present invention has an object to provide a polysiloxane which is a liquid substance having low viscosity, is excellent in curing workability, and has excellent heat resistance in an obtained cured material, and to a production method of a cured material using the polysiloxane. Specifically disclosed is a polysiloxane which is obtained by hydrolysis and polycondensation of a silicon compound having three hydrolyzable groups, a silicon compound having two hydrolyzable groups and a silicon compound having one hydrolyzable group, and is characterized by containing a hydrosilylatable carbon-carbon unsaturated group, a hydrosilyl group and an alkoxysilyl group, and having a number average molecular weight of 500 to 20,000.