Methane diffusion microflame was established on a stainless steel or copper tube burner with the inner (outer) diameter range from 0.7 (1.0) mm to 6 (8) mm and the methane flow rate range from 137 to 275 mm³/s. The temperature profile of burner surface and the heating heat flux to the wall above the burner were measured. Within the measurement conditions, the highest heating heat flux (6.8 W/cm²) was achieved by the SUS tube burner with an inner diameter of 0.7 mm at the distance of 6 mm from burner tip to the wall when methane flow rate was 275 mm³/s. It is shown that a thinner tube has higher burner temperature and higher heating heat flux, except for the copper tube burner with an inner diameter of 1.0 mm. In terms of the heating heat flux to the wall above the burner, the copper tube burner is more strongly affected by the tube size than SUS tube burner.