Disease diagnosis is the most important starting point for treatment. But in several life-threatening diseases, including cancer, conventional diagnostic methods have shown still limitations for efficient and effective di-agnosis. To overcome these problems, development of ‘novel biosensor’ for sensitive, rapid, facile, and accu-rate diagnosis has been highly required. This dissertation deals with the development of biosensors for cancer diagnosis, one is capture platform for circulating tumor cells (CTCs), and another is molecular beacon for mutation detection in cancer cells. CTCs have attracted much attention as promising markers for diagnosing and monitoring the cancer status. But the extremely rare number of the CTCs is present in blood with ex-tremely large number of other blood cells, capture of CTCs with high-efficiency and high-purity is technically challenging. In this dissertation, magnetic particle-based platforms were developed for efficient and effective capture of CTCs. Tentacle-structure magnetic particles enabled to obtain significantly increased capture effi-ciency and purity. Sequential targeting by quantum dots nanoparticles and magnetic beads allowed simultaneous capture and quantification of cancer cell. The results suggested that these platforms will be applied to CTC-based cancer diagnosis. To analysis of cancer cells in terms of mutation detection, PCR-based direct sequencing is most extensively used even though this method is labor-intensive, time-consuming and low-sensitivity. To consider this problem, this dissertation describes the molecular beacon (MB) for rapid, simple, and sensitive detection of harboring mutations in cancer cells in terms of exon 2 deleted-aminoacyl-tRNA synthetase complex-interacting multifunctional protein 2 (AIMP2-DX2). Dual-conjugated liposomes could discover the mutation by cancer cell-specific imaging. Lung cancer patients sample could be analyzed by molecular beacon based-assay. I believe that molecular beacon-based approach will provide the information regarding the patient status and therapeutic guideline.