PROBLEM TO BE SOLVED: To provide a metal particle-dispersed solution or the like capable of activating the surface of a base material to be joined even without using a dangerous gas such as a reducing gas upon heating-sintering.SOLUTION: Provided is a metal fine particle-dispersed solution formed by dispersing metal particles (P) including copper nanoparticles (P1) in which the average primary particle diameter is 2 to 500 nm into an organic solvent (S). The copper nanoparticles (P1) include at least one or more kinds of halogen components selected from the group consisting of chlorine of 100 to 2,100 ppm, bromine of 200 to 4,100 ppm and fluorine of 100 to 2,000 ppm in the range of the total content in which the value of C represented in specified formula reaches 1 or lower.SELECTED DRAWING: None
