A locking device for a drilling device comprising an outer tube provided with an inner shoulder, said locking device comprising: an elongated locking body comprising a lower part mountable in the outer tube and an elongated upper part; an unlocking tube mountable in the outer tube around the locking body and capable of sliding between a high actuated position and a low rest position, said unlocking tube comprising at least two elongated lateral openings (112, 114) distributed therearound; at least two latches (116, 118), each being fastened onto the locking body and comprising an operative end, each of the latches (116, 118) being capable of pivoting between a deployed position in which the operative end of the latch (116, 118) projects outside the unlocking tube from one of the corresponding openings (112, 114) to bear under the inner shoulder of the outer tube in order to lock the locking body to the outer tube and prevent its exit, and a retracted position in which the latch (116, 118) is retracted close to the locking body in order to unlock the locking body of the outer tube; a tubular piston slidably mounted vis-à-vis the locking body close to the operative ends of the latches (116,118) and being secured to the unlocking tube; and a compression spring mechanism mounted on the upper part of the locking body and pressing the piston towards the latches (116, 118) in order to maintain them in their deployed position so as to allow a drilling operation, wherein a traction exerted on the unlocking tube secured to the piston compresses the spring mechanism so as to prevent the piston from pressing onto the latches (116, 118) which are positioned in their retracted position in order to allow rising an element of the drilling device; characterized in that said latches (116, 118) are pivotally fastened on the locking body and in that the tubular piston is slidably mounted around the locking body. an elongated locking body comprising a lower part mountable in the outer tube and an elongated upper part; an unlocking tube mountable in the outer tube around the locking body and capable of sliding between a high actuated position and a low rest position, said unlocking tube comprising at least two elongated lateral openings (112, 114) distributed therearound; at least two latches (116, 118), each being fastened onto the locking body and comprising an operative end, each of the latches (116, 118) being capable of pivoting between a deployed position in which the operative end of the latch (116, 118) projects outside the unlocking tube from one of the corresponding openings (112, 114) to bear under the inner shoulder of the outer tube in order to lock the locking body to the outer tube and prevent its exit, and a retracted position in which the latch (116, 118) is retracted close to the locking body in order to unlock the locking body of the outer tube; a tubular piston slidably mounted vis-à-vis the locking body close to the operative ends of the latches (116,118) and being secured to the unlocking tube; and a compression spring mechanism mounted on the upper part of the locking body and pressing the piston towards the latches (116, 118) in order to maintain them in their deployed position so as to allow a drilling operation, wherein a traction exerted on the unlocking tube secured to the piston compresses the spring mechanism so as to prevent the piston from pressing onto the latches (116, 118) which are positioned in their retracted position in order to allow rising an element of the drilling device; characterized in that said latches (116, 118) are pivotally fastened on the locking body and in that the tubular piston is slidably mounted around the locking body.