Mechanical quantity measuring device and sensor unit

A mechanical quantity measuring device comprising:

• a sensor chip having a strain detector formed on a surface of a semiconductor substrate and a plurality of electrodes;
• a stem having a seat that protrudes from an adjacent peripheral portion and has an upper surface that is attached to a lower surface of the sensor chip by a bonding material formed from a metallic material or a glass material;
• a lead-out wiring part including a plurality of wires that are electrically connected to the plurality of electrodes;
• and
• a fixing part configured to fix the stem, wherein:
• the stem and the fixing part are metallically bonded to one another,
• the stem is a rectangular-shaped plate member,
• the seat has a rectangular shape larger than the sensor chip, and
• the sensor chip is bonded to the stem via the bonding material, the bonding material including solder containing Sn-3.5 wt %, Ag-0.5 wt %, or Au-20 wt %.