Laser-driven ultrafast X-ray sources are widely used for diagnostic radiography. However, there is a large divergence of fast electrons when they are generated by an intense short-pulse laser interacting with a foil target. We design a nanowire array target to achieve a more compact point X-ray source. Fast electrons are confined and guided by the nanowire array structure in order to generate a ${\mathrm{K}}_{\mathrm{\alpha }}$ source with a small spot size. In our work, the smallest measured source size is comparable to the laser spot size, while the conversion efficiency can reach $2.4\times {10}^4$.