A room-temperature-curable polyorganosiloxane composition, comprising: 100 parts by mass of a polyorganosiloxane mixture obtained by mixing 20 to 60 parts by mass of a polyorganosiloxane having two or more alkoxy groups bonded to silicon atoms in a molecule and a viscosity at 23°C of 3 mPa·s to 500 mPa·s, measured according to JIS K6249, and 80 to 40 parts by mass of a polyorganosiloxane represented by an average composition formula, having a weight-average molecular weight (Mw) of 2,000 to 100,000, measured by use of gel permeation chromatograph based on polystyrene, and a three-dimensional network structure, and being in a solid state or in a semisolid state at normal temperature, R 1 a Si(OR 2) b O {4-(a+b)}/2... where R 1 represents an unsubstituted monovalent hydrocarbon group or a monovalent hydrocarbon group in which part of hydrogen atoms is substituted by a halogen atom or a cyano-alkyl group, R 2 represents an alkyl group or an alkoxy-substituted alkyl group being an alkyl group in which part of hydrogen atoms is substituted by an alkoxy group, and a and b are positive numbers satisfying 0.5 ≤ a ≤ 1.5 and 0 < b < 3, and 0.1 to 15 parts by mass of an organic titanium compound as a curing catalyst. 100 parts by mass of a polyorganosiloxane mixture obtained by mixing 20 to 60 parts by mass of a polyorganosiloxane having two or more alkoxy groups bonded to silicon atoms in a molecule and a viscosity at 23°C of 3 mPa·s to 500 mPa·s, measured according to JIS K6249, and 80 to 40 parts by mass of a polyorganosiloxane represented by an average composition formula, having a weight-average molecular weight (Mw) of 2,000 to 100,000, measured by use of gel permeation chromatograph based on polystyrene, and a three-dimensional network structure, and being in a solid state or in a semisolid state at normal temperature, R 1 a Si(OR 2) b O {4-(a+b)}/2... where R 1 represents an unsubstituted monovalent hydrocarbon group or a monovalent hydrocarbon group in which part of hydrogen atoms is substituted by a halogen atom or a cyano-alkyl group, R 2 represents an alkyl group or an alkoxy-substituted alkyl group being an alkyl group in which part of hydrogen atoms is substituted by an alkoxy group, and a and b are positive numbers satisfying 0.5 ≤ a ≤ 1.5 and 0 < b < 3, and 20 to 60 parts by mass of a polyorganosiloxane having two or more alkoxy groups bonded to silicon atoms in a molecule and a viscosity at 23°C of 3 mPa·s to 500 mPa·s, measured according to JIS K6249, and 80 to 40 parts by mass of a polyorganosiloxane represented by an average composition formula, having a weight-average molecular weight (Mw) of 2,000 to 100,000, measured by use of gel permeation chromatograph based on polystyrene, and a three-dimensional network structure, and being in a solid state or in a semisolid state at normal temperature, R 1 a Si(OR 2) b O {4-(a+b)}/2... where R 1 represents an unsubstituted monovalent hydrocarbon group or a monovalent hydrocarbon group in which part of hydrogen atoms is substituted by a halogen atom or a cyano-alkyl group, R 2 represents an alkyl group or an alkoxy-substituted alkyl group being an alkyl group in which part of hydrogen atoms is substituted by an alkoxy group, and a and b are positive numbers satisfying 0.5 ≤ a ≤ 1.5 and 0 < b < 3, and 0.1 to 15 parts by mass of an organic titanium compound as a curing catalyst.