An electrophotographic photosensitive member, comprising: a support having a metallic surface, an undercoat layer directly on the metallic surface of the support, and a photosensitive layer on the undercoat layer, wherein, the undercoat layer comprises: metal oxide particles whose surface is treated with a silane compound represented by the following formula, and an urethane resin obtained by polymerization of an isocyanate compound and a polyvinyl acetal resin, and a modulus of elastic deformation (we/wt) of a surface of the undercoat layer satisfies the following formula, the modulus of elastic deformation being measured by the universal hardness test according to the description: (value of we/wt of surface of undercoat layer measured under 23°C, 50% RH environment after keeping under same environment for 24 hours) ≥ (value of we/wt of surface of undercoat layer measured under 23°C, 50% RH environment after keeping under 50°C, 90% RH environment for 24 hours), wherein, in the formula, R 1, R 2, and R 3 each independently represent an alkyl group having 1 to 3 carbon atoms, R 4 represents a divalent group represented by one of the following formulas (R4-1), (R4-2), and (R4-3), and R 5 represents a hydrogen atom, a phenyl group, or an alkyl group having 1 to 3 carbon atoms, and wherein, in the formulas (R4-1), (R4-2), and (R4-3), m is an integer number selected from 1 to 3, and R 6 and R 7 each independently represent an alkylene group having 1 to 4 carbon atoms. a support having a metallic surface, an undercoat layer directly on the metallic surface of the support, and a photosensitive layer on the undercoat layer, wherein, the undercoat layer comprises: metal oxide particles whose surface is treated with a silane compound represented by the following formula, and an urethane resin obtained by polymerization of an isocyanate compound and a polyvinyl acetal resin, and metal oxide particles whose surface is treated with a silane compound represented by the following formula, and an urethane resin obtained by polymerization of an isocyanate compound and a polyvinyl acetal resin, and a modulus of elastic deformation (we/wt) of a surface of the undercoat layer satisfies the following formula, the modulus of elastic deformation being measured by the universal hardness test according to the description: (value of we/wt of surface of undercoat layer measured under 23°C, 50% RH environment after keeping under same environment for 24 hours) ≥ (value of we/wt of surface of undercoat layer measured under 23°C, 50% RH environment after keeping under 50°C, 90% RH environment for 24 hours), wherein, in the formula, R 1, R 2, and R 3 each independently represent an alkyl group having 1 to 3 carbon atoms, R 4 represents a divalent group represented by one of the following formulas (R4-1), (R4-2), and (R4-3), and R 5 represents a hydrogen atom, a phenyl group, or an alkyl group having 1 to 3 carbon atoms, and wherein, in the formulas (R4-1), (R4-2), and (R4-3), m is an integer number selected from 1 to 3, and R 6 and R 7 each independently represent an alkylene group having 1 to 4 carbon atoms. R 1, R 2, and R 3 each independently represent an alkyl group having 1 to 3 carbon atoms, R 4 represents a divalent group represented by one of the following formulas (R4-1), (R4-2), and (R4-3), and R 5 represents a hydrogen atom, a phenyl group, or an alkyl group having 1 to 3 carbon atoms, and m is an integer number selected from 1 to 3, and R 6 and R 7 each independently represent an alkylene group having 1 to 4 carbon atoms.