Conjugated oligonucleotides attract interest from various areas such as medicine and nanotechnology. Common synthetic methods, however, rely on heterogeneous coupling strategies that often give low yield. This report describes a new synthetic strategy for conjugated oligonucleotides using an alkyl-chain-soluble support, which allows high-yielding conjugation with various reporter molecules in homogeneous environment. Furthermore, we demonstrated efficient biconjugation due to successive introduction of thiol and amine into one linker.