This study was designed to evaluate the effect of high pressure treatment on the extraction properties of deodeok (Codonopsis lanceolata) as measured by total phenols, flavonoids, phenolic acids, radical scavenging activity, and cytotoxicity. deodeok was subjected to different pressure levels (0.1-500 MPa) and extraction times (0-30 min). The highest amounts of total phenols and flavonoids were 648 and 130 ${mu}g$ RE/mL at 300 MPa for 20 min, respectively. The optimizing conditions for the pressure-assisted water extraction (PAWE) of deodeok as a function of pressure level and extraction time were 385 MPa and 25 min for total phenols (633 ${mu}g$ GAE/mL) and 405 MPa and 24 min for flavonoids (124 ${mu}g$ RE/mL). The PAWE significantly increased the amount of vanillic acid (41 ${mu}g/mL$) in deodeok extract compared to the conventional extraction (CE, 17 ${mu}g/mL$). The highest radical scavenging activity (81%) of deodeok extract was achieved at the treatment of 500 MPa and 30 min. The PAWE can increase biologically active components in deodeok by considering process variables such as pressure level and extraction time. The results provide useful information towards improving pharmaceutical properties of medicinal plants and herbs using the PAWE.