A process for formation of a copper plating film, which comprises immersing a material to be plated, which is susceptible to deposition of copper, in an electroless copper plating solution comprising copper ions, a reducing agent, a pH-adjusting agent, a trialkanolmonoamine or a salt thereof in an amount sufficient to act as a complexing agent and accelerator, an iron ion compound selected from the group consisting of at least one of ferrous halide salts, ferric halide salts, ferrocyanide compounds and ferric cyanide compounds as a reaction initiator, and at least one compound selected from the group consisting of pyridazine methylpiperidine, 1,2-di-(2-pyridyl)ethylene, 1,2-di-(pyridyl)ethylene, 2,2'-dipyridylamine, 2,2'-bipyridyl, 2,2'-bipyrimidine, 6,6'-dimethyl-2,2'-dipyridyl, di-2-pyridylketone, N,N,N',N'-tetraethylethylenediame, naphthalene, 1,8-naphthyridine, 1,6-naphthyridine, tetrathiafurvalene, .alpha.,.alpha.,.alpha.-terpyridine, phthalic acid, isophthalic acid and 2,2'-dibenzoic acid as an agent for effecting physical properties of said plating film, to thereby deposit said copper on a surface of the material to be plated at a deposition speed higher than the copper deposition speed obtained when the trialkanolamine or salt thereof is present in amount sufficient to complex the copper ion but not enough to function as the accelerator, wherein (i) said iron ion compound is present in an amount of at least 2.4.times.10.sup.-4 mole/liter (100 mg/liter) and said agent for effecting the physical properties is present in an amount of at least 3.2.times.10.sup.-4 mole/liter (50 mg/liter);
- (ii) said iron ion compound is present in an amount of at least 1.2.times.10.sup.-4 mole/liter (50 mg/liter) and said agent for effecting the physical properties is present in an amount of 6.4.times.10.sup.-4 mole/liter (100 mg/liter);
- or (iii) said iron ion compound is present in an amount of 7.2.times.10.sup.-4 mole/liter (300 mg/liter) and said agent for effecting the physical properties is present in an amount of at least 1.9.times.10.sup.-4 mole/liter (30 mg/liter).