To quantitatively analyze the positioning error due to the ionosphere over the Korean peninsula, we created 2-dimensional ionosphere map using 44 permanent Global Positioning System(GPS) stations operated by Ministry of Land, Transport, and Maritime Affairs. We estimated Vertical Total Electron Content(VTEC) in a fine rectangular grids of $0.1^{circ}{ imes}0.1^{circ}$ resolution. The observables we used were phase-leveled pseudoranges which are linear combinations of pseudoranges and carrier phases. VTECs were computed for five days during January 25-29, 2003 using the data from 45 permanent stations. In comparison with the Global Ionosphere Map of the Center for Orbit Determination in Europe, RMS differences were at the level of 8 TECU(TEC Unit).