N-Arylphenylacetamide derivatives represented by the following formula [I]: (wherein R<1 >is C1-6 alkoxy, etc.; R<2 >is hydrogen, -(CH2)m-N(R<6>)(R<7>) (m is an integer of from 1 to 4; R<6 >is hydrogen, C1-4 alkyl, etc., R<7 >is hydrogen, etc.), etc.; R<3 >is hydrogen, halogen, etc.; R<4 >is C6-10 alkyl, -Y-R<8 >(Y is a single bond, C1-6 alkylene, C2-6 alkenylene, C2-6 alkynylene, etc., R<8 >is aryl, C3-8 cycloalkyl, C6-15 polycycloalkyl, etc.), etc.; R<5 >is hydrogen, etc.; and X<1 >is hydrogen), or pharmaceutically acceptable salts thereof or hydrates or solvates of the same, and a pharmaceutical composition containing the same. These compounds are useful as preventives and/or remedies giving no pain at the early stage of administration, which are efficacious in oral administration and have potent analgesic and antiinflammatory effects.