Endoscope system and operating method thereof

A light source device simultaneously produces violet narrowband light and green narrowband light. A complementary color type imaging device of a complementary color type endoscope outputs first to fourth mixed pixel signals. In a complementary color second processor, a matrix operation unit performs a matrix operation of the first to fourth mixed pixel signals, and produces first and second display signals D1 and D2. A mixed color corrector corrects the first and second display signals D1 and D2 on the basis of relational expressions of "D1′=D1−K2×D2" and "D2′=D2−K1×D1". K1 represents the ratio of a signal value of the second display signal to a signal value of the first display signal under independent application of only the violet narrowband light. K2 represents the ratio of a signal value of the first display signal to a signal value of the second display signal under independent application of only the green narrowband light.