The present invention addresses the problem of providing a novel, solid silver-copper alloy. Provided is a solid silver-copper alloy in which the concentration of copper contained in the silver-copper alloy is 0.1-99.94 wt %, and which has, as the principal constituent thereof, a non-eutectic structure which does not contain a eutectic when the solid silver-copper alloy is at room temperature. This silver-copper alloy can be produced by mixing a fluid containing silver ions and copper ions with a fluid containing a reducing agent, and separating silver-copper alloy particles therefrom. It is preferable to mix the fluid containing the silver ions and copper ions with the fluid containing the reducing agent in a thin-film fluid formed between processing surfaces arranged so as to face one another, capable of approaching toward and separating from one another, and capable of having at least one surface rotate relative to the other. The diameter of the particles of the silver-copper alloy is preferably 50 nm or less. This solid silver-metal alloy may also be a solid alloy comprising one or more types of other metals in addition to silver and copper.