When copper powder manufactured by a wet reduction method is kneaded with resin in a high filling rate, it is difficult to maintain a low viscosity. The invention is to solve the problem of high viscosity without changing the characteristics such as particle size and specific surface area of the copper powder obtained by a wet reduction method. This invention relates to copper powder for an electrically conductive paste wherein copper powder manufactured by a wet reduction method is subjected to a surface-flattening treatment in which the particles are mechanically collided each other.