Understanding the reason for the divertor flow asymmetry in heliotron/torsatron-type fusion devices is important for the safety of the in-vessel components, such as divertor plates subject to the direct impact of the plasma or the electrical probes and thermocouples for measurements of the particle and energy fluxes to the divertor plates. In previous work, the divertor flow distributions were studied mainly with focusing on the up-down asymmetry in a heliotron-type fusion device, Heliotron E. This paper analyzes the in-out asymmetry of divertor flows and discusses the effects on this asymmetry of the magnetic axis position (the horizontal shift due to variation of the vertical magnetic field or plasma pressure) and power of neutral beams.