A MEMS device chip manufacturing method including a grinding step of grinding a device forming area of a wafer to thereby form a recess and an annular reinforcing portion surrounding the recess, a MEMS device forming step of performing any processing including etching to the wafer after performing the grinding step to thereby form a plurality of MEMS devices partitioned by a plurality of crossing division lines in the device forming area, and a dividing step of dividing the wafer along the division lines after performing the MEMS device forming step to thereby manufacture a plurality of MEMS device chips.