Hand milling machine for machining the surface of a floor or wall, comprising: a machine body having a housing for receiving a tool rotatable about a tool axis (A W), and a holding handle fixed to the housing for holding the machine body and defining a working plane (E A) to which the tool axis (A W) extends in parallel; a guide handle for guiding the hand milling machine, characterized in that the guide handle extends at an angle (α) inclined to the working plane (E A) and is pivotally mounted on the housing about a pivot axis (A S) to adjust the angle (α); and in that the hand milling machine comprises a locking device for locking the guide handle relative to the working plane (E A); the locking device having a locking body which comprises at least two recesses of spherical segmental shape which are arranged along a circular path and represent positions in which the locking device locks the guide handle relative to the working plane (E A); wherein the detent has a locking element configured for positive engagement in one of the recesses and having the shape of a ball; wherein the detent has a pull rod comprising a retaining element configured for retaining the locking element in the recess; wherein the retaining element has a constriction at least partially receiving the locking element; and wherein the retaining element is movably mounted by means of the tension rod in such a way that in an unactuated state of the tension rod the locking element is retained in the recess by the retaining element and in an actuated state of the tension rod the locking element escapes from the recess into the constriction and releases the recess. a machine body having a housing for receiving a tool rotatable about a tool axis (A W), and a holding handle fixed to the housing for holding the machine body and defining a working plane (E A) to which the tool axis (A W) extends in parallel; a guide handle for guiding the hand milling machine, characterized in that the guide handle extends at an angle (α) inclined to the working plane (E A) and is pivotally mounted on the housing about a pivot axis (A S) to adjust the angle (α); and in that the hand milling machine comprises a locking device for locking the guide handle relative to the working plane (E A); the locking device having a locking body which comprises at least two recesses of spherical segmental shape which are arranged along a circular path and represent positions in which the locking device locks the guide handle relative to the working plane (E A); wherein the detent has a locking element configured for positive engagement in one of the recesses and having the shape of a ball; wherein the detent has a pull rod comprising a retaining element configured for retaining the locking element in the recess; wherein the retaining element has a constriction at least partially receiving the locking element; and wherein the retaining element is movably mounted by means of the tension rod in such a way that in an unactuated state of the tension rod the locking element is retained in the recess by the retaining element and in an actuated state of the tension rod the locking element escapes from the recess into the constriction and releases the recess.