This paper presents a three-dimensional deformable microfilter modified with a nucleic-acid aptamer for capturing of target cells. Separating and capturing target cells from the fluid is very important for health diagnosis and medical diagnosis by liquid biopsy. The presented microfilter permits the separation of arbitrary size because the opening gap of the microfilter is three-dimensionally transformed by fluidic force. The deformation of the microfilter is able to be changed by adjusting the fluidic force. Also, the presented microfilter permits the specific capturing of target cells by specifically adsorbing ability of a nucleic-acid aptamer. In this experiment, the cancer cell was used as a target cell. The nucleic-acid aptamer that has a specific adsorbing ability to epithelial cell adhesion molecules was used for capturing the cancer cell. The results of experiment, the target cells were effectively captured by nucleic-acid aptamer modified microfilter.