An optical subassembly manufacturing method includes forming connecting electrodes and a piece of high-melting-point glass on a wiring substrate; positioning on and connecting to the connecting electrodes, an optoelectronic converting element; disposing on the piece of high-melting-point glass, a piece of low-melting-point glass having a melting point lower than the piece of high-melting-point glass; and fixing to the piece of low-melting-point glass, a protruding portion of a lens member further having a lens portion. The protruding portion has a shape matching that of the piece of high-melting-point glass, and relative positions of the protruding portion and the optical axis of the lens portion are determined to correspond to relative positions of the connecting electrodes and the piece of high-melting-point glass. The fixing includes fixing the protruding portion of the lens member to the piece of high-melting-point glass via surface tension generated by melting the piece of low-melting-point glass.