Solid titanium catalyst component, olefin polymerization catalyst, olefin polymerization method, and propylene polymer

A solid titanium catalyst component (I) comprising titanium, magnesium, halogen, and a cyclic multiple-ester-group-containing compound (a) represented by the following formula (1):

• wherein n1 to n4 are each independently an integer of 0 to 2, m is 0 or 1, and x is an integer of 0 to 10, with a relationship of m+x≥1 being satisfied;
• R1 and R2 are each independently a substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms;
• R3 to R16 and R are each independently a hydrogen atom, a substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms, or a halogen atom;
• a hydrogen atom, a carbon atom, or both, of R1 to R16 and R are optionally replaced by at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, a phosphorus atom, a halogen atom, and a silicon atom;
• and two or more selected from R3 to R16 and R are optionally bonded to one another to form a monocyclic or polycyclic ring, and adjacent substituents are optionally directly bonded to form a multiple bond;
• Ca, Cb, and Cc are carbon atoms, and in a carbon-carbon bond of a cyclic structure formed of Ca, Cb, and Cc, R bonded to adjacent carbon are optionally directly bonded to one another to form a multiple bond;
• and
• A is a single bond or a divalent linking group having a chain with a length of 1 to 3 atoms between two free radicals,
• wherein any two or more of R3-R10 may be absent on adjacent carbon atoms, and a bond between adjacent carbon atoms where two or more of R3-R10 are absent may comprise a double carbon-carbon bond or a triple carbon-carbon bond;
• and
• wherein R may be absent on any two or more of adjacent carbon atoms, and a bond between adjacent carbon atoms where R is absent may comprise a double carbon-carbon bond or a triple carbon-carbon bond.