A hydraulic circuit of a construction machine including a plurality of center bypass passages (RC, RC1, RC2), into which a pressurized oil discharged from a plurality of hydraulic pumps (P, P1, P2) is supplied, the hydraulic circuit comprising: a directional control valve group (Gv) including a plurality of directional control valves (V, Va1, Va2, Vb1, Vb2, Vbk, Vsw, Vop, Vt1, Vt2, Vst) that are arranged in tandem with the center bypass passages (RC, RC1, RC2); a bleed-off valve (Vbo) arranged on a downstream side of each center bypass passage (RC, RC1, RC2) relative to the directional control valve group (Gv); and a merging circuit (RJ, RJa, RJb) that merges the pressurized oil supplied into one center bypass passage of the plurality of center bypass passages (RC, RC1, RC2) and the pressurized oil in another center bypass passage of the plurality of center bypass passages (RC, RC1, RC2), wherein each directional control valve (V, Va1, Va2, Vb1, Vb2, Vbk, Vsw, Vop, Vt1, Vt2, Vst) includes a first internal passage that flows the pressurized oil supplied into the directional control valve out into the center bypass passages (RC, RC1, RC2), and a second internal passage that supplies the pressurized oil supplied to the directional control valve to a hydraulic actuator of the construction machine, wherein the center bypass passages (RC, RC1, RC2) and the first internal passage form a parallel passage where the first internal passage flows the pressurized oil discharged from the hydraulic pump (P, P1, P2) out onto downstream sides of the center bypass passages (RC, RC1, RC2) relative to the directional control valve, wherein the bleed-off valve (Vbo) performs a bleed-off control for the pressurized oil supplied through the parallel passage by changing an opening area of the bleed-off valve (Vbo), wherein the merging circuit (RJ, RJa, RJb) includes a merging directional control valve (Vj) that controls an inflow direction of the pressurized oil to be merged. a directional control valve group (Gv) including a plurality of directional control valves (V, Va1, Va2, Vb1, Vb2, Vbk, Vsw, Vop, Vt1, Vt2, Vst) that are arranged in tandem with the center bypass passages (RC, RC1, RC2); a bleed-off valve (Vbo) arranged on a downstream side of each center bypass passage (RC, RC1, RC2) relative to the directional control valve group (Gv); and a merging circuit (RJ, RJa, RJb) that merges the pressurized oil supplied into one center bypass passage of the plurality of center bypass passages (RC, RC1, RC2) and the pressurized oil in another center bypass passage of the plurality of center bypass passages (RC, RC1, RC2), wherein each directional control valve (V, Va1, Va2, Vb1, Vb2, Vbk, Vsw, Vop, Vt1, Vt2, Vst) includes a first internal passage that flows the pressurized oil supplied into the directional control valve out into the center bypass passages (RC, RC1, RC2), and a second internal passage that supplies the pressurized oil supplied to the directional control valve to a hydraulic actuator of the construction machine, a first internal passage that flows the pressurized oil supplied into the directional control valve out into the center bypass passages (RC, RC1, RC2), and a second internal passage that supplies the pressurized oil supplied to the directional control valve to a hydraulic actuator of the construction machine, wherein the center bypass passages (RC, RC1, RC2) and the first internal passage form a parallel passage where the first internal passage flows the pressurized oil discharged from the hydraulic pump (P, P1, P2) out onto downstream sides of the center bypass passages (RC, RC1, RC2) relative to the directional control valve, wherein the bleed-off valve (Vbo) performs a bleed-off control for the pressurized oil supplied through the parallel passage by changing an opening area of the bleed-off valve (Vbo), wherein the merging circuit (RJ, RJa, RJb) includes a merging directional control valve (Vj) that controls an inflow direction of the pressurized oil to be merged.