Electrochemical cells are widely used for hydrogen production by electrochemical water splitting (EWS). Even though much progress in the electrochemical cells has been made, the mainstream device architecture is limited to batch-type configuration which leads to increased volume and extra need of products separation. Thus, it is still desirable to develop an electrochemical cell with a monolithic device architecture. Herein, we report a monolithic electrochemical cell (MEC) consisting of Pt nanoparticles (NPs) and FeNi3/Fe3O4 hybrid NPs anchored to laser induced graphene (LIG) electrodes directly patterned on both sides of polyimide film. When serving as an individual electrode, Pt/LIG and FeNi3/Fe3O4/LIG exhibit overpotentials of 90 mV and 253 mV at 10 mA/cm(2) for HER and OER, respectively. When they are assembled as a MEC for EWS, it displays a voltage of 1.58 V at 10 mA/cm(2). This novel device architecture omits the need of multiple assembling steps for manufacturing the full cells. In addition, the rapid and continuous laser synthesis strategy is quite simple, economic, and easily scaled up, which offers numbers of advantages over traditional batch-to-batch methods and thus offering a universal route to fabricating MECs via in-situ synthesis of various electrocatalysts embedded in LIG electrodes for other electrochemical reactions.