We propose a useful method to boost the imaging speed for spectral domain optical coherence tomography (SDOCT) by multiplying a number of high-speed spectrometers used in the system with selective precise control of data-recording and data-reading phases for spectral cameras employed in each spectrometer. To demonstrate the proposed method, we use two spectrometers built in a 1310 nm-band SDOCT system, each equipped with a high-speed InGaAs line-scan camera capable of 92-kHz line-scan rate, to achieve an unprecedented imaging speed at 184,000 lines/s. We validate the multiplied imaging speed by measuring Doppler-induced phase shift in the spectrograms using a flow phantom.