We have developed a microchannel device and a technique for automated microinjection, through which DNA molecules can be delivered to living cells. Microinjection is a reliable way of introducing DNA and various compounds for new drugs into many kinds of cells. However, it is tedious because all the operations, such as holding each cell with a micropipette, positioning it, and injecting the materials, have to be done manually. This is why we have developed the microchannel device and use it in conjunction with the cell manipulation and trapping techniques. Cells flow in a suspension liquid and are trapped when suctioned through a microhole at the bottom of the microchannel. We can automatically trap cells and inject individual DNA molecules. The microchannel device is made of a 100 x 50 mm cross section of silicon rubber. A micro hole is drilled to a minimum diameter of 3mm by excimer laser ablation on a polycarbonate plate. A glass capillary filled with DNA is inserted in the trapped cell from the upper side of the microchannel. We verified the basic operation of the microchannel device in an experiment using white blood corpuscles (K562 cell line) of about 15mm in diameter.