We have developed a pulse injection method of DNA oligomer aqueous solution onto Cu(111) surfaces as a new sample-preparation technique for scanning tunneling microscopy (STM) studies of biomolecules. The STM images revealed that the surface of Cu(111) retains its atomic flatness even after the injection of DNA-containing solution and that the deposition of intact DNA oligomers without aggregation is possible. The observed internal structure of deposited DNA suggests the promising possibility of sequencing DNA by means of STM. In order to examine the possibility of manipulation of DNA, translational positioning of DNA oligomer has been performed by a lateral pushing of the DNA with scanning tip.