A silica membrane filter comprising a porous substrate and a silica membrane provided on a surface of the porous substrate, wherein the silica membrane contains an aryl group and/or an alkyl group, wherein at least one of conditions (i), (ii) and (iii) is satisfied: (i) the ratio of the He gas permeation amount to the N 2 gas permeation amount (He gas permeation amount / N 2 gas permeation amount) is 1.0 to 2.6, and the ratio of the N 2 gas permeation amount to the SF 6 gas permeation amount (N 2 gas permeation amount / SF 6 gas permeation amount) is 1.5 to 5.0, and the silica membrane contains an alkyl group; (ii) the ratio of a He gas permeation amount to an N 2 gas permeation amount (He gas permeation amount / N 2 gas permeation amount) is 1.0 to 2.6, and the ratio of the N 2 gas permeation amount to a SF 6 gas permeation amount (N 2 gas permeation amount / SF 6 gas permeation amount) is 1.5 to 10, and the silica membrane contains an aryl group, the aryl group being one of a phenyl group, a benzyl group, a tolyl group, and a xylyl group; (iii) the ratio of a He gas permeation amount to an N 2 gas permeation amount (He gas permeation amount / N 2 gas permeation amount) is 1.0 to 2.6, and the ratio of the N 2 gas permeation amount to a SF 6 gas permeation amount (N 2 gas permeation amount / SF 6 gas permeation amount) is 1.5 to 10, and the silica membrane contains an alkyl group, the alkyl group having a carbon number of 2 to 8, and wherein the He gas permeation amount, the N 2 gas permeation amount and the SF 6 gas permeation amount are determined by subjecting the silica membrane filter to a gas permeation test for He gas, N 2 gas and SF 6 gas, the gas permeation test being performed with maintaining the temperature of the silica membrane filter and the He gas, N 2 gas and SF 6 gas supplied to the silica membrane filter at 25°C, the He gas, N 2 gas, and SF 6 gas being supplied to the silica membrane filter in a state of appropriately applying a fixed pressure in the range from 0.01 MPa to 5 MPa, and determining the gas permeation amounts of He gas, N 2 gas and SF 6 gas. wherein the silica membrane contains an aryl group and/or an alkyl group, wherein at least one of conditions (i), (ii) and (iii) is satisfied: (i) the ratio of the He gas permeation amount to the N 2 gas permeation amount (He gas permeation amount / N 2 gas permeation amount) is 1.0 to 2.6, and the ratio of the N 2 gas permeation amount to the SF 6 gas permeation amount (N 2 gas permeation amount / SF 6 gas permeation amount) is 1.5 to 5.0, and the silica membrane contains an alkyl group; (ii) the ratio of a He gas permeation amount to an N 2 gas permeation amount (He gas permeation amount / N 2 gas permeation amount) is 1.0 to 2.6, and the ratio of the N 2 gas permeation amount to a SF 6 gas permeation amount (N 2 gas permeation amount / SF 6 gas permeation amount) is 1.5 to 10, and the silica membrane contains an aryl group, the aryl group being one of a phenyl group, a benzyl group, a tolyl group, and a xylyl group; (iii) the ratio of a He gas permeation amount to an N 2 gas permeation amount (He gas permeation amount / N 2 gas permeation amount) is 1.0 to 2.6, and the ratio of the N 2 gas permeation amount to a SF 6 gas permeation amount (N 2 gas permeation amount / SF 6 gas permeation amount) is 1.5 to 10, and the silica membrane contains an alkyl group, the alkyl group having a carbon number of 2 to 8, (i) the ratio of the He gas permeation amount to the N 2 gas permeation amount (He gas permeation amount / N 2 gas permeation amount) is 1.0 to 2.6, and the ratio of the N 2 gas permeation amount to the SF 6 gas permeation amount (N 2 gas permeation amount / SF 6 gas permeation amount) is 1.5 to 5.0, and the silica membrane contains an alkyl group; (ii) the ratio of a He gas permeation amount to an N 2 gas permeation amount (He gas permeation amount / N 2 gas permeation amount) is 1.0 to 2.6, and the ratio of the N 2 gas permeation amount to a SF 6 gas permeation amount (N 2 gas permeation amount / SF 6 gas permeation amount) is 1.5 to 10, and the silica membrane contains an aryl group, the aryl group being one of a phenyl group, a benzyl group, a tolyl group, and a xylyl group; (iii) the ratio of a He gas permeation amount to an N 2 gas permeation amount (He gas permeation amount / N 2 gas permeation amount) is 1.0 to 2.6, and the ratio of the N 2 gas permeation amount to a SF 6 gas permeation amount (N 2 gas permeation amount / SF 6 gas permeation amount) is 1.5 to 10, and the silica membrane contains an alkyl group, the alkyl group having a carbon number of 2 to 8, and wherein the He gas permeation amount, the N 2 gas permeation amount and the SF 6 gas permeation amount are determined by subjecting the silica membrane filter to a gas permeation test for He gas, N 2 gas and SF 6 gas, the gas permeation test being performed with maintaining the temperature of the silica membrane filter and the He gas, N 2 gas and SF 6 gas supplied to the silica membrane filter at 25°C, the He gas, N 2 gas, and SF 6 gas being supplied to the silica membrane filter in a state of appropriately applying a fixed pressure in the range from 0.01 MPa to 5 MPa, and determining the gas permeation amounts of He gas, N 2 gas and SF 6 gas.