A method of designing a drilling pattern for excavating a rock cavern, the drilling pattern determining at least the locations and hole direction angles of drill holes in the coordinate system of the drilling pattern and the lengths of the drill holes for a round to be drilled at a tunnel face; the method comprising: computer-aided designing of the drilling pattern by means of a drilling pattern design program; determination of a navigation plane for the drilling pattern; determination of starting locations at the navigation plane for the holes to be drilled; determination of at least an excavation profile for the cavern to be excavated, at least one group of holes being located inside the excavation profile, and determination of the length of the drilling pattern on the basis of the length of the round to be excavated; determination of a plurality of drill holes for each group of holes; and determination of the directions of the holes to be drilled from the starting locations to the bottoms of the holes; determining, in the drilling pattern, a blast plane located at the bottom of the round at a distance corresponding to the length of the pattern from the navigation plane; placing drill hole bottom locations at the bottom of the round at the blast plane; characterized by performing blasting calculation at the blast plane for at least some holes in the drilling pattern; utilizing in the blasting calculation mutual dependencies between burden, hole spacing, specific charge (q) and degree of charge stored in advance in a memory, and blasting-technical data about the specific charge (q) and the degree of charge stored in advance in a memory; and supplying one of the following drill hole properties to the drilling pattern design program: drill hole start location at navigation plane, drill hole direction, whereby the given drill hole property is a first drill hole property, and determining a missing second drill hole property from the mentioned drill hole start location and drill hole direction not being supplied on the basis of the location of the drill hole bottom and the first, given property, whereby the drill hole properties being determined are viewed from the bottom of the round towards the navigation plane since the locations of the drill hole bottoms are determined before the starting locations and directions. computer-aided designing of the drilling pattern by means of a drilling pattern design program; determination of a navigation plane for the drilling pattern; determination of starting locations at the navigation plane for the holes to be drilled; determination of at least an excavation profile for the cavern to be excavated, at least one group of holes being located inside the excavation profile, and determination of the length of the drilling pattern on the basis of the length of the round to be excavated; determination of a plurality of drill holes for each group of holes; and determination of the directions of the holes to be drilled from the starting locations to the bottoms of the holes; determining, in the drilling pattern, a blast plane located at the bottom of the round at a distance corresponding to the length of the pattern from the navigation plane; placing drill hole bottom locations at the bottom of the round at the blast plane; characterized by performing blasting calculation at the blast plane for at least some holes in the drilling pattern; utilizing in the blasting calculation mutual dependencies between burden, hole spacing, specific charge (q) and degree of charge stored in advance in a memory, and blasting-technical data about the specific charge (q) and the degree of charge stored in advance in a memory; and supplying one of the following drill hole properties to the drilling pattern design program: drill hole start location at navigation plane, drill hole direction, whereby the given drill hole property is a first drill hole property, and determining a missing second drill hole property from the mentioned drill hole start location and drill hole direction not being supplied on the basis of the location of the drill hole bottom and the first, given property, whereby the drill hole properties being determined are viewed from the bottom of the round towards the navigation plane since the locations of the drill hole bottoms are determined before the starting locations and directions.