This paper demonstrates welding the tip of an ultrathin Pt wire to the side of a similar wire by Joule heating. The tip of the wire, with a diameter of 600-800 nm, is brought into contact with the side of another wire, and they are welded together into a complex form by supplying a constant direct current through the parts in contact. The conditions for tip to side welding of Pt wires are compared to those of tip to tip welding using a parameter that was proposed previously for the tip to tip welding of two wires. The parameter depends on the current, the length and cross-sectional area of the wires and comprises a function with respect to the thermal boundary conditions. Although the successful welding conditions of tip to side welding are located in the range of those for tip to tip welding, the lower limit of the conditions for tip to side welding was slightly higher than that in tip to tip welding. Finally, a three-dimensional micrometer-scale structure was created by repeating the tip to side welding process.