Trolley jack comprising: - a main body; - a lifting element capable of moving up or down with respect to the main body; - an operating lever that can be lowered through which the user operates the lifting element; - interlocking means for fixing the operating lever in the operative position thereof; and - automatic release means actuated by a push element operated by the user for automatically releasing said operating lever so that it can be lowered on the main body; characterized in that - the interlocking means and automatic release means are located in a lever holder to which the lower end of said operating lever is fixed in a swiveling manner and in that said lever holder is partially introduced in the main body of the jack such that, when operated, it activates the hydraulic mechanism responsible for causing the lifting element to move up,. - the lever holder is formed as a hollow tubular body open at its two ends which internally comprises: - a rigid elongated body extending from a little over half of the height thereof to the lower end thereof, protruding therethrough; and - a latch located at the upper end which can move longitudinally along the inside thereof from a lower position in which it abuts with the upper end of the elongated body, to an upper position in which it protrudes partially through the upper edge of the lever holder. where: - the operating lever has a cavity intended for housing the latch when the operating lever is interlocked in the lever holder, - the latch is kept on the upper edge of the lever holder and separated from the elongated body by the action of an elastic element located between both, the push element is integrally attached to the latch which, when operated by the user, overcomes the resistance of the elastic element and pushes the latch in a direction such that it moves down to the lower part of the lever holder, and where - both an upper corner of the latch and an edge of the lower end of the operating lever are rounded for the purpose of reducing the friction between both when they contact one another in the operation of interlocking said operating lever in the lever holder; so that to interlock the lever holder the user can operate the push element to overcome the resistance of the elastic element and push the latch in a direction such that it moves down to the lower part of the lever holder instead of interlocking it overcoming the friction between the upper corner of the latch and the edge of the lower end. - a main body; - a lifting element capable of moving up or down with respect to the main body; - an operating lever that can be lowered through which the user operates the lifting element; - interlocking means for fixing the operating lever in the operative position thereof; and - automatic release means actuated by a push element operated by the user for automatically releasing said operating lever so that it can be lowered on the main body; - the interlocking means and automatic release means are located in a lever holder to which the lower end of said operating lever is fixed in a swiveling manner and in that said lever holder is partially introduced in the main body of the jack such that, when operated, it activates the hydraulic mechanism responsible for causing the lifting element to move up,. - the lever holder is formed as a hollow tubular body open at its two ends which internally comprises: - a rigid elongated body extending from a little over half of the height thereof to the lower end thereof, protruding therethrough; and - a latch located at the upper end which can move longitudinally along the inside thereof from a lower position in which it abuts with the upper end of the elongated body, to an upper position in which it protrudes partially through the upper edge of the lever holder. - a rigid elongated body extending from a little over half of the height thereof to the lower end thereof, protruding therethrough; and - a latch located at the upper end which can move longitudinally along the inside thereof from a lower position in which it abuts with the upper end of the elongated body, to an upper position in which it protrudes partially through the upper edge of the lever holder. - the operating lever has a cavity intended for housing the latch when the operating lever is interlocked in the lever holder, - the latch is kept on the upper edge of the lever holder and separated from the elongated body by the action of an elastic element located between both, the push element is integrally attached to the latch which, when operated by the user, overcomes the resistance of the elastic element and pushes the latch in a direction such that it moves down to the lower part of the lever holder, and where - both an upper corner of the latch and an edge of the lower end of the operating lever are rounded for the purpose of reducing the friction between both when they contact one another in the operation of interlocking said operating lever in the lever holder;