A casted cylinder block that has been cast by using a mold, comprising: a cylinder bore wall part having a plurality of cylinder bores aligned along a first direction; a water jacket groove having a groove bottom and arranged on an outer periphery of the cylinder bore wall part so as to surround the cylinder bore wall part; and a water jacket external wall part arranged on an outer periphery of the water jacket groove, and defines the water jacket groove together with the cylinder bore wall part, wherein: the water jacket groove includes a shallow groove part where the groove depth becomes shallower toward an end of the cylinder bore wall part in the alignment direction of the plurality of cylinder bores; a portion of the water jacket external wall part where the shallow groove part is formed includes a first inner wall surface facing the water jacket groove and a first outer wall surface on an opposite side to the first inner wall surface; and when from among the groove depth directions the direction in which the groove becomes deeper is taken to be the downward direction, a portion of the cylinder bore wall part where the shallow groove part is arranged has a second outside wall surface facing the water jacket groove, and a third outside wall surface arranged in the downward direction from the groove bottom and constituting the outside wall surface of the cylinder block together with the first outer wall surface of the water jacket external wall part, the third outside wall surface being depressed towards a cylinder bore with respect to the first outer wall surface, characterized in that: the mold corresponding to the cylinder bore wall part is formed with a melt supply sprue and a melt discharge outlet at portions corresponding to two ends of the cylinder block in the alignment direction of the cylinder bores, such that a melt flows from a first end of the cylinder bore wall part to a second end of the cylinder bore wall part in the alignment direction of the cylinder bores; the shallow groove part is arranged in the region near the melt discharge outlet; and the groove depth of the shallow groove part is shallowest at the end of the cylinder block in the alignment of the plurality of cylinder bores. a cylinder bore wall part having a plurality of cylinder bores aligned along a first direction; a water jacket groove having a groove bottom and arranged on an outer periphery of the cylinder bore wall part so as to surround the cylinder bore wall part; and a water jacket external wall part arranged on an outer periphery of the water jacket groove, and defines the water jacket groove together with the cylinder bore wall part, wherein: the water jacket groove includes a shallow groove part where the groove depth becomes shallower toward an end of the cylinder bore wall part in the alignment direction of the plurality of cylinder bores; a portion of the water jacket external wall part where the shallow groove part is formed includes a first inner wall surface facing the water jacket groove and a first outer wall surface on an opposite side to the first inner wall surface; and when from among the groove depth directions the direction in which the groove becomes deeper is taken to be the downward direction, a portion of the cylinder bore wall part where the shallow groove part is arranged has the water jacket groove includes a shallow groove part where the groove depth becomes shallower toward an end of the cylinder bore wall part in the alignment direction of the plurality of cylinder bores; a portion of the water jacket external wall part where the shallow groove part is formed includes a first inner wall surface facing the water jacket groove and a first outer wall surface on an opposite side to the first inner wall surface; and when from among the groove depth directions the direction in which the groove becomes deeper is taken to be the downward direction, a portion of the cylinder bore wall part where the shallow groove part is arranged has a second outside wall surface facing the water jacket groove, and a third outside wall surface arranged in the downward direction from the groove bottom and constituting the outside wall surface of the cylinder block together with the first outer wall surface of the water jacket external wall part, the third outside wall surface being depressed towards a cylinder bore with respect to the first outer wall surface, characterized in that: the mold corresponding to the cylinder bore wall part is formed with a melt supply sprue and a melt discharge outlet at portions corresponding to two ends of the cylinder block in the alignment direction of the cylinder bores, such that a melt flows from a first end of the cylinder bore wall part to a second end of the cylinder bore wall part in the alignment direction of the cylinder bores; the shallow groove part is arranged in the region near the melt discharge outlet; and the groove depth of the shallow groove part is shallowest at the end of the cylinder block in the alignment of the plurality of cylinder bores. the mold corresponding to the cylinder bore wall part is formed with a melt supply sprue and a melt discharge outlet at portions corresponding to two ends of the cylinder block in the alignment direction of the cylinder bores, such that a melt flows from a first end of the cylinder bore wall part to a second end of the cylinder bore wall part in the alignment direction of the cylinder bores; the shallow groove part is arranged in the region near the melt discharge outlet; and the groove depth of the shallow groove part is shallowest at the end of the cylinder block in the alignment of the plurality of cylinder bores.