An oscillator circuit includes an initial level setting circuit configured to operate in an on-state during an initial operation of the oscillator circuit to supply a first level voltage to a first node and a second level voltage to a second node, a switching circuit configured to connect a power supply voltage terminal and a ground terminal to the first or second node in response to first and second clock signals having different phases after the initial operation, a signal generation circuit connected between the first and second nodes and configured to perform charging and discharging operations based on a potential difference between the first and second nodes, and generate first and second voltages determined by the charging and discharging operations, and an inverter circuit configured to generate the first clock signal based on the first voltage, and generate the second clock signal based on the second voltage.