Disclosed is an electronic ballast for a high intensity discharge lamp which is capable of reducing the number of parts to thereby maintain a high power factor and prevent power loss generated in the circuit thereof. The electronic ballast includes: a converter part (2) having first to fourth rectifying diodes (D1-D4), a choke coil (TR2) and a first condenser (C4); an inverter part (3) having first and second switching transistors (K1, K2), a second condenser (C13), a DIAC (D11), and first and second gate wave shaping integrated circuits (IC1, IC2); an output matching part (4) having a resonant coil (TR4), first to third resonant condensers (C7-C9), and a transformer (TR3); an absorbed DC power source part (5) having first and second diodes (D7, D8) and third and fourth condensers (C5,C6); a power control part (6) having a first operational amplifier (U2), first and second DC voltage detection resistors (R8, R9), a first resistor (R15), a second operational amplifier (U1), a second resistor (R7), a third resistor (R6), a first comparator (U3), a fourth resistor (R11), a second comparator (U4), a fifth resistor (R14), a first switch (SW1), a third comparator (U5), a timer, a sixth resistor (R16), a fifth condenser (C15) and an undervoltage lockout; and a gate transformer (TR5).