An engine combustion chamber structure comprising: a combustion chamber of an engine, the combustion chamber being formed by a lower face of a cylinder head, a cylinder, and a crown face of a piston; and a fuel injection valve that injects fuel into the combustion chamber, wherein the crown face of the piston is provided with a cavity and a flat rim provided near an outer circumferential rim of the crown face, the fuel injection valve injects fuel toward the cavity and is disposed at or near a radial center of the combustion chamber, the cavity includes a first cavity that is provided in a radially central region of the crown face and includes a first bottom having a first depth in a cylinder axial direction, a second cavity that is provided in the crown face to be in an outer side of an outer circumference of the first cavity and includes a second bottom having a second depth in the cylinder axial direction, the second depth being smaller than the first depth, a connecting portion that connects the first cavity to the second cavity, a standing wall region disposed further in a radially outer side than the second bottom of the second cavity, and a second upper end that is a highest portion of the second cavity and located in the radially outer most of the second cavity, the second bottom is provided lower than an upper end, regarding a cylinder axial direction, of the connecting portion, and a lower section of the standing wall region is provided further in a radially inner side than an upper edge of the standing wall region, characterized in that, in a cross-section including a cylinder axis, a portion of the second cavity from the second bottom to an upper edge of the standing wall region is a quarter-arc having a first radius, the second upper end is formed of a quarter-arc having a second radius, and a lower end of the second upper end adjoins the upper edge of the standing wall region and a top end of the second upper end adjoins the flat rim. a combustion chamber of an engine, the combustion chamber being formed by a lower face of a cylinder head, a cylinder, and a crown face of a piston; and a fuel injection valve that injects fuel into the combustion chamber, wherein the crown face of the piston is provided with a cavity and a flat rim provided near an outer circumferential rim of the crown face, the fuel injection valve injects fuel toward the cavity and is disposed at or near a radial center of the combustion chamber, the cavity includes a first cavity that is provided in a radially central region of the crown face and includes a first bottom having a first depth in a cylinder axial direction, a second cavity that is provided in the crown face to be in an outer side of an outer circumference of the first cavity and includes a second bottom having a second depth in the cylinder axial direction, the second depth being smaller than the first depth, a connecting portion that connects the first cavity to the second cavity, a standing wall region disposed further in a radially outer side than the second bottom of the second cavity, and a second upper end that is a highest portion of the second cavity and located in the radially outer most of the second cavity, a first cavity that is provided in a radially central region of the crown face and includes a first bottom having a first depth in a cylinder axial direction, a second cavity that is provided in the crown face to be in an outer side of an outer circumference of the first cavity and includes a second bottom having a second depth in the cylinder axial direction, the second depth being smaller than the first depth, a connecting portion that connects the first cavity to the second cavity, a standing wall region disposed further in a radially outer side than the second bottom of the second cavity, and a second upper end that is a highest portion of the second cavity and located in the radially outer most of the second cavity, the second bottom is provided lower than an upper end, regarding a cylinder axial direction, of the connecting portion, and a lower section of the standing wall region is provided further in a radially inner side than an upper edge of the standing wall region, characterized in that, in a cross-section including a cylinder axis, a portion of the second cavity from the second bottom to an upper edge of the standing wall region is a quarter-arc having a first radius, the second upper end is formed of a quarter-arc having a second radius, and a lower end of the second upper end adjoins the upper edge of the standing wall region and a top end of the second upper end adjoins the flat rim.