A data output circuit of a semiconductor device includes: a pattern data generation unit configured to generate pattern data in response to a bank selection signal, a variable delay unit configured to delay a source signal, which is generated in response to the bank selection signal, by a delay time corresponding to a delay control signal, a pattern control signal generation unit configured to generate a pattern control signal in response to an output signal of the variable delay unit, and a delay time control block configured to generate the delay control signal in response to the phases of the pattern control signal and the pattern data.