An α-substituted phenylacetic acid derivative useful as an agricultural fungicide, represented by general formula (I), or a salt thereof, a process for producing the same, an intermediate for the production thereof, and an agricultural fungicide containing the same as the active ingredient, wherein R 1 represents halogen, alkyl, OH, alkylthio, alkylsulfinyl, alkylsulfonyl, amino or nitro; Q represents aryl, heterocycle, mono- or disubstituted methyleneamino, (substituted amino-)methyl, alkyl, alkenyl, alkynyl, substituted carbonyl or substituted sulfonyl; X represents hydrogen, halogen, alkyl or OH; Y represents OH, alkylthio or amino; Z represents oxygen or sulfur; M represents oxygen, S(O)i (i being 0, 1 or 2), NR 2 (R 2 being hydrogen, alkyl or acyl) or a single bond; and n represents 0, 1 or 2.