A positive resist composition comprising: an alkali-soluble polymer containing a unit structure represented by Formula: (in Formula 2, R 1 represents a halogen atom, an alkyl group, an alkoxy group, a thiol group, a cyano group, an amino group, an amide group, an alkylcarbonyl group or a thioalkyl group, R 3 represents a hydrogen atom or a methyl group, m3 represents an integer of 1 or 2, when m3 = 1, m1 represents an integer of 0 to 7, when m3 = 2, m1 represents an integer of 0 to 9), and a unit structure represented by Formula: (in Formula, R 4 and R 5 individually represent a hydrogen atom, a methyl group, a carboxyl group or an alkylenecarboxyl group having 1 to 3 carbon atom(s), Q represents a single bond, an alkylene group having 1 to 3 carbon atom(s) or an aromatic group having 6 to 10 carbon atoms); wherein when the total number of all unit structures constituting the polymer is assumed to be 1.0, the ratio of the number n2 of unit structures represented by Formula and the ratio of the number n3 of unit structures represented by Formula satisfy 0.2≤n2≤0.8, 0.1≤n3≤0.7, and 0.3≤n2+n3≤1.0; and a compound having an organic group which undergoes photodecomposition to yield an alkali-soluble group, wherein the compound has a structure represented by Formula: (in Formula, R 11 represents a hydrogen atom, a 1,2-quinonediazide group or a derivative thereof, R 12 represents an unsubstituted or substituted alkyl group having 1 to 10 carbon atom(s), a halogen atom or an alkoxy group having 1 to 10 carbon atom(s), m4 represents an integer of 0 or 1, when m4 is 0, m5 represents an integer of 1 to 5 and m6 represents an integer satisfying 0≤m6≤(5-m5) when m4 is 1, m5 represents an integer of 1 to 7 and m6 represents an integer satisfying 0≤m6≤(7-m5), and in all -OR 11 groups existing in the compound, R 11 is a 1,2-quinonediazide group or a derivative thereof in an amount of 10 to 98 mol%); and a crosslinkable compound selected from the compounds represented by Formulae, and an alkali-soluble polymer containing a unit structure represented by Formula: (in Formula 2, R 1 represents a halogen atom, an alkyl group, an alkoxy group, a thiol group, a cyano group, an amino group, an amide group, an alkylcarbonyl group or a thioalkyl group, R 3 represents a hydrogen atom or a methyl group, m3 represents an integer of 1 or 2, when m3 = 1, m1 represents an integer of 0 to 7, when m3 = 2, m1 represents an integer of 0 to 9), R 1 represents a halogen atom, an alkyl group, an alkoxy group, a thiol group, a cyano group, an amino group, an amide group, an alkylcarbonyl group or a thioalkyl group, R 3 represents a hydrogen atom or a methyl group, m3 represents an integer of 1 or 2, when m3 = 1, m1 represents an integer of 0 to 7, when m3 = 2, m1 represents an integer of 0 to 9), and a unit structure represented by Formula: (in Formula, R 4 and R 5 individually represent a hydrogen atom, a methyl group, a carboxyl group or an alkylenecarboxyl group having 1 to 3 carbon atom(s), Q represents a single bond, an alkylene group having 1 to 3 carbon atom(s) or an aromatic group having 6 to 10 carbon atoms); wherein when the total number of all unit structures constituting the polymer is assumed to be 1.0, the ratio of the number n2 of unit structures represented by Formula and the ratio of the number n3 of unit structures represented by Formula satisfy 0.2≤n2≤0.8, 0.1≤n3≤0.7, and 0.3≤n2+n3≤1.0; and a compound having an organic group which undergoes photodecomposition to yield an alkali-soluble group, wherein R 4 and R 5 individually represent a hydrogen atom, a methyl group, a carboxyl group or an alkylenecarboxyl group having 1 to 3 carbon atom(s), Q represents a single bond, an alkylene group having 1 to 3 carbon atom(s) or an aromatic group having 6 to 10 carbon atoms); wherein when the total number of all unit structures constituting the polymer is assumed to be 1.0, the ratio of the number n2 of unit structures represented by Formula and the ratio of the number n3 of unit structures represented by Formula satisfy 0.2≤n2≤0.8, 0.1≤n3≤0.7, and 0.3≤n2+n3≤1.0; and a compound having an organic group which undergoes photodecomposition to yield an alkali-soluble group, wherein the compound has a structure represented by Formula: (in Formula, R 11 represents a hydrogen atom, a 1,2-quinonediazide group or a derivative thereof, R 12 represents an unsubstituted or substituted alkyl group having 1 to 10 carbon atom(s), a halogen atom or an alkoxy group having 1 to 10 carbon atom(s), m4 represents an integer of 0 or 1, when m4 is 0, m5 represents an integer of 1 to 5 and m6 represents an integer satisfying 0≤m6≤(5-m5) when m4 is 1, m5 represents an integer of 1 to 7 and m6 represents an integer satisfying 0≤m6≤(7-m5), and in all -OR 11 groups existing in the compound, R 11 is a 1,2-quinonediazide group or a derivative thereof in an amount of 10 to 98 mol%); and a crosslinkable compound selected from the compounds represented by Formulae, and R 11 represents a hydrogen atom, a 1,2-quinonediazide group or a derivative thereof, R 12 represents an unsubstituted or substituted alkyl group having 1 to 10 carbon atom(s), a halogen atom or an alkoxy group having 1 to 10 carbon atom(s), m4 represents an integer of 0 or 1, when m4 is 0, m5 represents an integer of 1 to 5 and m6 represents an integer satisfying 0≤m6≤(5-m5) when m4 is 1, m5 represents an integer of 1 to 7 and m6 represents an integer satisfying 0≤m6≤(7-m5), and in all -OR 11 groups existing in the compound, R 11 is a 1,2-quinonediazide group or a derivative thereof in an amount of 10 to 98 mol%); and a crosslinkable compound selected from the compounds represented by Formulae, and