We investigated the magnetoconductivity ∆σ(H,T) defined by a function of magnetic field H and temperature T for three-dimensional indium–gallium–zinc oxide films in the resistivity ρ range of 0.076×10−3Ωm≤ρ(2.0K)≤0.55×10−3Ωm. Here, ∆σ(H,T) is the ∆σ(H,T)≡1/ρ(H,T)−1/ρ(0,T). With increasing ρ, the contribution ∆σEEI due to the electron–electron interaction (EEI) effect overcomes the contribution ∆σWL due to the weak localization (WL) effect. The sign of ∆σ(H)=∆σEEI+∆WL changes from positive to negative with increasing magnetic field, particularly at low temperatures. To perform a systematic investigation of ∆σEEI, we obtained the contribution of ∆σEEI using the relation ∆σEEI(H,T)=∆σexp.(H,T)−∆σWLtheo.(H,T), where ∆σWLtheo.(H,T) is estimated by fitting the WL theory to data at low magnetic fields. It was found that i) ΔσEEIHT/T as a function of H/T for each film collapses onto a single universal curve at a magnetic field of up to 5T and in the temperature range between 2.0 and 50K. ii) From the analyses of ΔσEEIHT/T in the high and low H/T regions with the EEI theory, the screening factors F∆σ,H and F∆σ,L were estimated, respectively. iii) The F∆σ,H values satisfy the theoretical prediction as 0<F<1. iv) With increasing ρ, the magnitudes of both F∆σ,H and F∆σ,L essentially decrease to approach 0 at ρc≈1.3×10−3Ωm, where the metal–insulator transition is suggested to occur.