One of the purposes of the present invention is to provide a condensation-curable silicone resin composition which show a less increase of the viscosity during handling and cures quickly to provide a cured product which has a very small amount of a remaining catalyst and which has high heat resistance and high light resistance. Thus, the present invention is to provide a condensation-curable silicone composition comprising the following components (A) to (C): (A) 100 parts by mass of an organopolysiloxane which has a branched or network structure and has two or more hydrolyzable groups each bonded to a silicon atom and at least one of (R1SiO3/2) and (SiO4/2) units, wherein R1 is, independently of each other, a hydrogen atom or a substituted or unsubstituted, monovalent hydrocarbon group having 1 to 12 carbon atoms, (B) 5 to 500 parts by mass of a linear organopolysiloxane having at least one hydrolyzable group bonded to a silicon atom at each of both terminals, and (C) at least one silazane compound represented by the following general formula (3) or (5) or comprising the following units (6) in an amount of 0.02 to 30 parts by mass, relative to total 100 parts by mass of components (A) and (B):