Flux and solder paste

A flux comprising:

• rosin;
• a polymer (P) having a repeating unit represented by General Formula (p1);
• a solvent;
• a thixotropic agent containing polyamide;
• a dicarboxylic acid represented by General Formula (c1);
• and
• a compound having a benzotriazole skeleton, which is selected from the group consisting of a compound represented by General Formula (AZ1-1) and a compound represented by General Formula (AZ1-2),
• wherein R1 represents a methyl group or a hydrogen atom, and R2 represents a hydrocarbon group having 1 or 2 carbon atoms or a hydrogen atom,
• wherein R represents an alkylene group having 1 to 10 carbon atoms, a phenylene group, or a single bond, provided that a methylene group constituting the alkylene group may be substituted with an oxygen atom,
• wherein R11 represents an organic group or a hydrogen atom, R12 represents a substituent, n1 represents an integer in a range of 0 to 4, R21 represents an organic group or a hydrogen atom, R22 represents a substituent, and n2 represents an integer in a range of 0 to 4.