To provide a flux which enhances wettability of a solder, is excellent in temperature cycle reliability, and can suppress scattering by heating during reflow, and a solder paste using the same.SOLUTION: A flux contains an organic acid, an acrylic resin, a rosin, a thixotropic agent and a solvent, and contains no water. In the flux, the organic acid contains 1,2,3-propane tricarboxylic acid, a content of the 1,2,3-propane tricarboxylic acid is 0.1 mass% or more and 15 mass% or less, a content of the acrylic resin is 5 mass% or more and 45 mass% or less, and a content of the rosin is 5 mass% or more and 45 mass% or less.SELECTED DRAWING: None