The manipulation and direct mechanical measurement of single DNA molecule could give much information about its elastic properties. Single stranded DNA (ssDNA) of 100 bases was adsorbed onto flat gold surface fabricated by depositing gold onto mica surface. Atomic force microscope (AFM) was used to observe the surface topography with different ssDNA concentration. Then the ssDNAs were stretched by AFM tip and in 50% cases ssDNAs could be stretched. Various kinds of force curves have been observed due to the different interaction between AFM tip and ssDNAs.