Grazing incidence optics used in soft X-ray microscopes require supersmooth surface and highly accurate figure. We considered the fabrication of a Wolter type I mirror, one of grazing incidence optics, with axial-symmetric inner reflecting surfaces using single-point diamond turning. Electroless nickel was chosen as reflecting material Cutting conditions for machining the inner reflecting surface were restricted because of long arm of a single-crystal diamond tool. The machined Wolter type I mirror had approximately 270 nm P-V in figure error and 3 nm Ra in surface roughness. The direct-machined Wolter type I mirror could be successfully used in a soft Xray microscope based on laser-produced X-ray source.