  We theoretically investigated a method to detect a single skyrmion in a
magnetic tunneling junction (MTJ) geometry. Using the tunneling Hamiltonian
approach, we calculated the tunneling magnetoresistance (TMR) ratio of the
skyrmion-ferromagnet bilayer system. We show the TMR ratio is determined sorely
by the spin profile of the skyrmion and geometrical factor of the device, if
only the system is reasonably clean such that the spectral broadening is
smaller than the exchange coupling between the local and the itinerant magnetic
moment. The TMR ratio in that case can amount to $30\%$ or higher when the
diameter of the skyrmion is as large as the size of the device. Since this
criterion is easily achievable in real systems, MTJ geometry can be a good
candidate of the electrical detection of a single skyrmion i.e., the reading
process of the information in the future skyrmionics memory devices.
