A machining center comprising: a bed structure deflected in a longitudinal direction (x) along a deflection curve, DC, by a load distribution thereon; a palette structure having a palette for selectively holding a standby workpiece and secured to a first end portion of the bed structure such that a palette loading is applied to the first end portion of the bed structure; a spindle assembly to which a machining tool is secured and secured to a second end portion opposite to the first end portion of the bed structure such that a spindle loading is applied to the second end portion of the bed structure; a table movably secured to the bed structure such that a machining workpiece is secured to the table and a table loading is applied to a load point of the bed structure; and an automatic aligner automatically detecting a first installation error (α 1) of the table and a second installation error (α 2) of the spindle assembly and automatically correcting the first and the second installation errors (α 1, α 2) such that the machining workpiece and the machining tool are aligned with each other, wherein the automatic aligner includes: a position detecting unit configured to detect bed heights of the bed structure at a minimal deflection point and a maximal deflection point of the deflection curve, respectively, and a process position of the bed structure at which the table is located, wherein the deflection curve is provided as a single continuous curve or as a plurality of discrete curves that are divided into bed sections of the bed structure; an error calculating unit configured to calculate the first and the second installation errors (α 1, α 2) according to the bed heights and the process position; and a driving unit configured to drive at least one of the table and the spindle assembly to correct the first and the second installation errors (α 1, α 2). a bed structure deflected in a longitudinal direction (x) along a deflection curve, DC, by a load distribution thereon; a palette structure having a palette for selectively holding a standby workpiece and secured to a first end portion of the bed structure such that a palette loading is applied to the first end portion of the bed structure; a spindle assembly to which a machining tool is secured and secured to a second end portion opposite to the first end portion of the bed structure such that a spindle loading is applied to the second end portion of the bed structure; a table movably secured to the bed structure such that a machining workpiece is secured to the table and a table loading is applied to a load point of the bed structure; and an automatic aligner automatically detecting a first installation error (α 1) of the table and a second installation error (α 2) of the spindle assembly and automatically correcting the first and the second installation errors (α 1, α 2) such that the machining workpiece and the machining tool are aligned with each other, wherein the automatic aligner includes: a position detecting unit configured to detect bed heights of the bed structure at a minimal deflection point and a maximal deflection point of the deflection curve, respectively, and a process position of the bed structure at which the table is located, wherein the deflection curve is provided as a single continuous curve or as a plurality of discrete curves that are divided into bed sections of the bed structure; an error calculating unit configured to calculate the first and the second installation errors (α 1, α 2) according to the bed heights and the process position; and a driving unit configured to drive at least one of the table and the spindle assembly to correct the first and the second installation errors (α 1, α 2). a position detecting unit configured to detect bed heights of the bed structure at a minimal deflection point and a maximal deflection point of the deflection curve, respectively, and a process position of the bed structure at which the table is located, wherein the deflection curve is provided as a single continuous curve or as a plurality of discrete curves that are divided into bed sections of the bed structure; an error calculating unit configured to calculate the first and the second installation errors (α 1, α 2) according to the bed heights and the process position; and a driving unit configured to drive at least one of the table and the spindle assembly to correct the first and the second installation errors (α 1, α 2).