Flaky copper powder, process for producing the same, and conductive paste

It is an object of the present invention to provide a flaky copper powder composed of fine particles having a sharp distribution particle size, a large crystallite diameter and high oxidation resistance. The flaky copper powder of the present invention contains P and has a crystallite diameter/D 1A ratio of 0.01 or more to achieve the object. The method for producing the flaky copper powder comprises four steps: a first step of preparing an aqueous solution containing a copper salt and complexing agent; a second step of adding an alkali hydroxide to the aqueous solution to prepare a first slurry containing cupric oxide; a third step of adding a first reducing agent which can reduce the cupric oxide into cuprous oxide to the first slurry to prepare a second slurry containing cuprous oxide; and a fourth step of adding a second reducing agent which can reduce the cuprous oxide into copper to the second slurry to provide a flaky copper powder, wherein phosphoric acid and its salt are added in at least one of the first to third steps and/or in the second slurry in the fourth step.